User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:85.0) Gecko/20100101 Firefox/85.0

Steps to reproduce:

IIRC Bug 1662558 enabled WebRender for me by default on Fenix Nightly, a few days ago.

But in today's Fenix Nightly (201117 20:41) WR is disabled and I don't seem to be able to enable manually

about:support says:
Compositing OpenGL
WEBRENDER unavailable by runtime:Failed to render WebRender
There's a lot of force-enabled stuff which I don't understand, I don't think I've messed with about:config that much ;)

Android 10.0, Samsung Galaxy A40 (Mali-G71)

Thanks

Full about:support below

Application Basics

Name Firefox Nightly
Version 85.0a1
Build ID 20201117094406
Distribution ID
User Agent Mozilla/5.0 (Android 10; Mobile; rv:85.0) Gecko/85.0 Firefox/85.0
OS Linux 29 #1 SMP PREEMPT Thu Sep 10 14:45:58 KST 2020
Multiprocess Windows 0/0
Fission Windows 0/0 Disabled by default
Remote Processes 1
Google Location Service Key Found
Google Safebrowsing Key Found
Mozilla Location Service Key Found
Safe Mode false
Crash Reports for the Last 3 Days

Report ID Submitted
Nightly Features

Name Version ID
Remote Processes

Type Count
Web Content 1 / 3
Add-ons

Name Type Version Enabled ID
Mozilla Android Components - Ads extension 67.0.20201117165227.1117211623 true ads@mozac.org
Mozilla Android Components - Browser Icons extension 67.0.20201117165227.1117165930 true icons@mozac.org
Mozilla Android Components - Cookies extension 67.0.20201117165227.1117211623 true cookies@mozac.org
Mozilla Android Components - Firefox Accounts WebChannel extension 67.0.20201117165227.1117165823 true fxa@mozac.org
Mozilla Android Components - ReaderView extension 67.0.20201117165227.1117170003 true readerview@mozac.org
Mozilla Android Components - Web Compatibility Interventions extension 17.0.0 true webcompat@mozilla.org
Mozilla Android Components - WebCompat Reporter extension 2.0.0 true webcompat-reporter@mozilla.org
uBlock Origin extension 1.30.6 true uBlock0@raymondhill.net
Google Search Fixer extension 1.6 false {58c32ac4-0d6c-4d6f-ae2c-96aaf8ffcb66}
Graphics

Features
Compositing OpenGL
Asynchronous Pan/Zoom touch input enabled; autoscroll enabled; smooth pinch-zoom enabled
WebGL 1 Driver WSI Info EGL_VENDOR: Android
EGL_VERSION: 1.4 Android META-EGL
EGL_EXTENSIONS: EGL_KHR_get_all_proc_addresses EGL_ANDROID_presentation_time EGL_KHR_swap_buffers_with_damage EGL_ANDROID_get_native_client_buffer EGL_ANDROID_front_buffer_auto_refresh EGL_ANDROID_get_frame_timestamps EGL_EXT_surface_SMPTE2086_metadata EGL_EXT_surface_CTA861_3_metadata EGL_KHR_image EGL_KHR_image_base EGL_EXT_image_gl_colorspace EGL_KHR_gl_colorspace EGL_KHR_gl_texture_2D_image EGL_KHR_gl_texture_cubemap_image EGL_KHR_gl_renderbuffer_image EGL_KHR_fence_sync EGL_KHR_create_context EGL_KHR_config_attribs EGL_KHR_surfaceless_context EGL_EXT_create_context_robustness EGL_ANDROID_image_native_buffer EGL_KHR_wait_sync EGL_ANDROID_recordable EGL_KHR_partial_update EGL_EXT_pixel_format_float EGL_KHR_mutable_render_buffer EGL_IMG_context_priority EGL_KHR_no_config_context
IsWebglOutOfProcessEnabled: 0
WebGL 1 Driver Renderer ARM -- Mali-G71
WebGL 1 Driver Version OpenGL ES 3.2 v1.r19p0-01rel0.###other-sha0123456789ABCDEF0###
WebGL 1 Driver Extensions GL_EXT_debug_marker GL_ARM_rgba8 GL_ARM_mali_shader_binary GL_OES_depth24 GL_OES_depth_texture GL_OES_depth_texture_cube_map GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_EXT_read_format_bgra GL_OES_compressed_paletted_texture GL_OES_compressed_ETC1_RGB8_texture GL_OES_standard_derivatives GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_EGL_image_external_essl3 GL_OES_EGL_sync GL_OES_texture_npot GL_OES_vertex_half_float GL_OES_required_internalformat GL_OES_vertex_array_object GL_OES_mapbuffer GL_EXT_texture_format_BGRA8888 GL_EXT_texture_rg GL_EXT_texture_type_2_10_10_10_REV GL_OES_fbo_render_mipmap GL_OES_element_index_uint GL_EXT_shadow_samplers GL_OES_texture_compression_astc GL_KHR_texture_compression_astc_ldr GL_KHR_texture_compression_astc_hdr GL_KHR_texture_compression_astc_sliced_3d GL_KHR_debug GL_EXT_occlusion_query_boolean GL_EXT_disjoint_timer_query GL_EXT_blend_minmax GL_EXT_discard_framebuffer GL_OES_get_program_binary GL_OES_texture_3D GL_EXT_texture_storage GL_EXT_multisampled_render_to_texture GL_EXT_multisampled_render_to_texture2 GL_OES_surfaceless_context GL_OES_texture_stencil8 GL_EXT_shader_pixel_local_storage GL_ARM_shader_framebuffer_fetch GL_ARM_shader_framebuffer_fetch_depth_stencil GL_ARM_mali_program_binary GL_EXT_sRGB GL_EXT_sRGB_write_control GL_EXT_texture_sRGB_decode GL_EXT_texture_sRGB_R8 GL_EXT_texture_sRGB_RG8 GL_KHR_blend_equation_advanced GL_KHR_blend_equation_advanced_coherent GL_OES_texture_storage_multisample_2d_array GL_OES_shader_image_atomic GL_EXT_robustness GL_EXT_draw_buffers_indexed GL_OES_draw_buffers_indexed GL_EXT_texture_border_clamp GL_OES_texture_border_clamp GL_EXT_texture_cube_map_array GL_OES_texture_cube_map_array GL_OES_sample_variables GL_OES_sample_shading GL_OES_shader_multisample_interpolation GL_EXT_shader_io_blocks GL_OES_shader_io_blocks GL_EXT_tessellation_shader GL_OES_tessellation_shader GL_EXT_primitive_bounding_box GL_OES_primitive_bounding_box GL_EXT_geometry_shader GL_OES_geometry_shader GL_ANDROID_extension_pack_es31a GL_EXT_gpu_shader5 GL_OES_gpu_shader5 GL_EXT_texture_buffer GL_OES_texture_buffer GL_EXT_copy_image GL_OES_copy_image GL_EXT_shader_non_constant_global_initializers GL_EXT_color_buffer_half_float GL_EXT_color_buffer_float GL_EXT_YUV_target GL_OVR_multiview GL_OVR_multiview2 GL_OVR_multiview_multisampled_render_to_texture GL_KHR_robustness GL_KHR_robust_buffer_access_behavior GL_EXT_draw_elements_base_vertex GL_OES_draw_elements_base_vertex GL_EXT_protected_textures GL_EXT_buffer_storage GL_EXT_external_buffer GL_EXT_EGL_image_array
WebGL 1 Extensions ANGLE_instanced_arrays EXT_blend_minmax EXT_color_buffer_half_float EXT_float_blend EXT_sRGB MOZ_debug OES_element_index_uint OES_fbo_render_mipmap OES_standard_derivatives OES_texture_float OES_texture_half_float OES_texture_half_float_linear OES_vertex_array_object WEBGL_color_buffer_float WEBGL_compressed_texture_astc WEBGL_compressed_texture_etc WEBGL_compressed_texture_etc1 WEBGL_debug_renderer_info WEBGL_debug_shaders WEBGL_depth_texture WEBGL_lose_context
WebGL 2 Driver WSI Info EGL_VENDOR: Android
EGL_VERSION: 1.4 Android META-EGL
EGL_EXTENSIONS: EGL_KHR_get_all_proc_addresses EGL_ANDROID_presentation_time EGL_KHR_swap_buffers_with_damage EGL_ANDROID_get_native_client_buffer EGL_ANDROID_front_buffer_auto_refresh EGL_ANDROID_get_frame_timestamps EGL_EXT_surface_SMPTE2086_metadata EGL_EXT_surface_CTA861_3_metadata EGL_KHR_image EGL_KHR_image_base EGL_EXT_image_gl_colorspace EGL_KHR_gl_colorspace EGL_KHR_gl_texture_2D_image EGL_KHR_gl_texture_cubemap_image EGL_KHR_gl_renderbuffer_image EGL_KHR_fence_sync EGL_KHR_create_context EGL_KHR_config_attribs EGL_KHR_surfaceless_context EGL_EXT_create_context_robustness EGL_ANDROID_image_native_buffer EGL_KHR_wait_sync EGL_ANDROID_recordable EGL_KHR_partial_update EGL_EXT_pixel_format_float EGL_KHR_mutable_render_buffer EGL_IMG_context_priority EGL_KHR_no_config_context
IsWebglOutOfProcessEnabled: 0
WebGL 2 Driver Renderer ARM -- Mali-G71
WebGL 2 Driver Version OpenGL ES 3.2 v1.r19p0-01rel0.###other-sha0123456789ABCDEF0###
WebGL 2 Driver Extensions GL_EXT_debug_marker GL_ARM_rgba8 GL_ARM_mali_shader_binary GL_OES_depth24 GL_OES_depth_texture GL_OES_depth_texture_cube_map GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_EXT_read_format_bgra GL_OES_compressed_paletted_texture GL_OES_compressed_ETC1_RGB8_texture GL_OES_standard_derivatives GL_OES_EGL_image GL_OES_EGL_image_external GL_OES_EGL_image_external_essl3 GL_OES_EGL_sync GL_OES_texture_npot GL_OES_vertex_half_float GL_OES_required_internalformat GL_OES_vertex_array_object GL_OES_mapbuffer GL_EXT_texture_format_BGRA8888 GL_EXT_texture_rg GL_EXT_texture_type_2_10_10_10_REV GL_OES_fbo_render_mipmap GL_OES_element_index_uint GL_EXT_shadow_samplers GL_OES_texture_compression_astc GL_KHR_texture_compression_astc_ldr GL_KHR_texture_compression_astc_hdr GL_KHR_texture_compression_astc_sliced_3d GL_KHR_debug GL_EXT_occlusion_query_boolean GL_EXT_disjoint_timer_query GL_EXT_blend_minmax GL_EXT_discard_framebuffer GL_OES_get_program_binary GL_OES_texture_3D GL_EXT_texture_storage GL_EXT_multisampled_render_to_texture GL_EXT_multisampled_render_to_texture2 GL_OES_surfaceless_context GL_OES_texture_stencil8 GL_EXT_shader_pixel_local_storage GL_ARM_shader_framebuffer_fetch GL_ARM_shader_framebuffer_fetch_depth_stencil GL_ARM_mali_program_binary GL_EXT_sRGB GL_EXT_sRGB_write_control GL_EXT_texture_sRGB_decode GL_EXT_texture_sRGB_R8 GL_EXT_texture_sRGB_RG8 GL_KHR_blend_equation_advanced GL_KHR_blend_equation_advanced_coherent GL_OES_texture_storage_multisample_2d_array GL_OES_shader_image_atomic GL_EXT_robustness GL_EXT_draw_buffers_indexed GL_OES_draw_buffers_indexed GL_EXT_texture_border_clamp GL_OES_texture_border_clamp GL_EXT_texture_cube_map_array GL_OES_texture_cube_map_array GL_OES_sample_variables GL_OES_sample_shading GL_OES_shader_multisample_interpolation GL_EXT_shader_io_blocks GL_OES_shader_io_blocks GL_EXT_tessellation_shader GL_OES_tessellation_shader GL_EXT_primitive_bounding_box GL_OES_primitive_bounding_box GL_EXT_geometry_shader GL_OES_geometry_shader GL_ANDROID_extension_pack_es31a GL_EXT_gpu_shader5 GL_OES_gpu_shader5 GL_EXT_texture_buffer GL_OES_texture_buffer GL_EXT_copy_image GL_OES_copy_image GL_EXT_shader_non_constant_global_initializers GL_EXT_color_buffer_half_float GL_EXT_color_buffer_float GL_EXT_YUV_target GL_OVR_multiview GL_OVR_multiview2 GL_OVR_multiview_multisampled_render_to_texture GL_KHR_robustness GL_KHR_robust_buffer_access_behavior GL_EXT_draw_elements_base_vertex GL_OES_draw_elements_base_vertex GL_EXT_protected_textures GL_EXT_buffer_storage GL_EXT_external_buffer GL_EXT_EGL_image_array
WebGL 2 Extensions EXT_color_buffer_float EXT_float_blend MOZ_debug OVR_multiview2 WEBGL_compressed_texture_astc WEBGL_compressed_texture_etc WEBGL_compressed_texture_etc1 WEBGL_debug_renderer_info WEBGL_debug_shaders WEBGL_lose_context
Uses Tiling true
Uses Tiling (Content) true
Target Frame Rate 60
GPU #1
Active Yes
Description Model: SM-A405FN, Product: a40eea, Manufacturer: samsung, Hardware: exynos7904, OpenGL: ARM -- Mali-G71 -- OpenGL ES 3.2 v1.r19p0-01rel0.###other-sha0123456789ABCDEF0###
Vendor ID ARM
Device ID Mali-G71
Driver Version OpenGL ES 3.2 v1.r19p0-01rel0.###other-sha0123456789ABCDEF0###
RAM 0
Diagnostics
AzureCanvasBackend skia
AzureContentBackend skia
AzureFallbackCanvasBackend none
CMSOutputProfile Empty profile data
Display0 1080x2340
DisplayCount 1
TileHeight 512
TileWidth 512
Device Reset Trigger Device Reset
Decision Log
HW_COMPOSITING
available by default
force_enabled by user: Force-enabled by pref
OPENGL_COMPOSITING
available by default
force_enabled by user: Force-enabled by pref
WEBRENDER
available by default
force_enabled by user: Force enabled by pref
unavailable by runtime: Failed to render WebRender
WEBRENDER_QUALIFIED
available by default
WEBRENDER_COMPOSITOR
disabled by default: Disabled by default
WEBRENDER_PARTIAL
available by default
WEBRENDER_ANGLE
available by default
unavailable by env: OS not supported
WEBRENDER_DCOMP_PRESENT
available by default
disabled by user: User disabled via pref
unavailable by env: Requires Windows 10 or later
unavailable by runtime: Requires ANGLE
WEBRENDER_SOFTWARE
available by default
disabled by env: Overriden by qualified hardware
OMTP
disabled by default: Disabled by default
WEBGPU
disabled by default: Disabled by default
Failure Log
(#0) Error Failed to link shader program: brush_image The number of vertex shader storage blocks (1) is greater than the maximum number allowed (0).
(#12) Error wr_renderer_render: Shader(Link("brush_solid", ""))
(#13) Error wr_renderer_render: Shader(Link("brush_solid", ""))
(#14) Error Failed to link shader program: brush_image
(#15) Error Failed to link shader program: brush_solid
(#16) Error Failed to link shader program: brush_opacity
(#17) Error Failed to link shader program: brush_solid
(#18) Error Failed to link shader program: ps_text_run
(#19) Error wr_renderer_render: Shader(Link("brush_image", ""))
(#20) Error wr_renderer_render: Shader(Link("brush_solid", ""))
(#21) Error wr_renderer_render: Shader(Link("brush_opacity", ""))
(#22) Error wr_renderer_render: Shader(Link("brush_solid", ""))
(#23) Error wr_renderer_render: Shader(Link("ps_text_run", ""))
(#24) Error Failed to link shader program: brush_image
(#25) Error wr_renderer_render: Shader(Link("brush_image", ""))
(#26) Error Compositors might be mixed (5,2)
Media

Audio Backend opensl
Max Channels 2
Preferred Sample Rate 48000
Roundtrip latency (standard deviation) ...
Output Devices
Name Group Vendor State Preferred Format Channels Rate Latency
Enabled All default: S16LE, support: S16LE S16BE F32LE F32BE 2 default: 44100, support: 44100 - 44100 128 - 441
Input Devices
Name Group Vendor State Preferred Format Channels Rate Latency
Enabled All default: S16LE, support: S16LE S16BE F32LE F32BE 1 default: 44100, support: 44100 - 44100 128 - 441
Media Capabilities
Enumerate database
Environment Variables

Important Modified Preferences

browser.cache.disk.amount_written 864646
browser.cache.disk.capacity 524288
browser.cache.disk.filesystem_reported 1
dom.presentation.device.name SM-A405FN
dom.w3c_pointer_events.enabled true
extensions.lastAppVersion 85.0a1
gfx.webrender.all true
idle.lastDailyNotification 1605658048
media.gmp.storage.version.observed 1
network.trr.blocklist_cleanup_done true
privacy.purge_trackers.date_in_cookie_database 0
privacy.purge_trackers.last_purge 1605658056345
security.remote_settings.crlite_filters.checked 1605671733
security.remote_settings.intermediates.checked 1605585333
storage.vacuum.last.index 0
Important Locked Preferences

fission.autostart.session false
Accessibility

Activated false
Prevent Accessibility 0
Library Versions

Expected minimum version Version in use
NSPR 4.29 4.29
NSS 3.59 3.59
NSSSMIME 3.59 3.59
NSSSSL 3.59 3.59
NSSUTIL 3.59 3.59
Startup Cache

Disk Cache Path /data/user/0/org.mozilla.fenix/files/mozilla/da26a20f.default/startupCache/startupCache.8.little
Ignore Disk Cache false
Found Disk Cache on Init true
Wrote to Disk Cache false
Internationalization & Localization

Application Settings
Requested Locales ["en-GB"]
Available Locales ["an","ar","ast","az","be","bg","bn","br","bs","ca","cak","cs","cy","da","de","dsb","el","en-CA","en-GB","en-US","eo","es-AR","es-CL","es-ES","es-MX","et","eu","fa","ff","fi","fr","fy-NL","ga-IE","gd","gl","gn","gu-IN","he","hi-IN","hr","hsb","hu","hy-AM","id","is","it","ja","ka","kab","kk","kn","ko","lij","lo","lt","lv","ml","mr","ms","my","nb-NO","ne-NP","nl","nn-NO","oc","pa-IN","pl","pt-BR","pt-PT","rm","ro","ru","sk","sl","son","sq","sr","sv-SE","ta","te","th","tr","trs","uk","ur","uz","vi","wo","xh","zam","zh-CN","zh-TW"]
App Locales ["en-GB","en-US","en-CA"]
Regional Preferences ["en-GB"]
Default Locale "en-US"
Operating System
System Locales ["en-GB"]
Regional Preferences ["en-GB"]

On the same build ID (20201117094406) I had the exact same problem on desktop Linux.

This should have been fixed by the backout of bug 1640960.

@Jamie, re your question in bug 1678022:- Not fixed for me in today's Nightly (201118 17:04 Build #2015776395, I installed it at 0715 GMT 19 Nov). Same errors "WEBRENDER unavailable by runtime: Failed to render WebRender" and a list of "Failed to link shader program" stuff.

Fixed in today's Nightly (201119 17:01). Thanks