User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:99.0) Gecko/20100101 Firefox/99.0

Steps to reproduce:

I force-enabled the WebRender compositor (gfx.webrender.compositor, gfx.webrender.compositor.force-enabled) on sway with the experimental wlroots Vulkan renderer (WLR_RENDERER=vulkan).
Versions:

• Firefox 99.0b8
• sway version 1.8-dev-fb3330c1 (Mar 27 2022, branch 'master')
• wlroots master 0.15.0-135-g4519117a
• mesa 21.3.7
• Linux 5.16.8
• Intel GPU - OpenGL renderer string: Mesa Intel(R) HD Graphics 620 (KBL GT2)

This issue was originally reported as a wlroots bug, but I was told it's most likely a Firefox bug so I'm reporting it here as well.
Link: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3404

Note: I've redacted some unrelated information in the attached about:support output.

Actual results:

At some point during startup, the Firefox quits suddenly and the following error is reported by sway:
[ERROR] [wlr] [render/vulkan/texture.c:403] Format 34325241 (AR24) can't be used with modifier ffffffffffffff
The error might occur only during loading of a specific page (I always have a lot of tabs open so it's not clear if a specific page was the culprit).

Expected results:

Firefox should work with the WebRender compositor enabled on the wlroots Vulkan renderer, same as the normal wlroots renderer.

The Bugbug bot thinks this bug should belong to the 'Core::Graphics: WebRender' component, and is moving the bug to that component. Please correct in case you think the bot is wrong.

Right, the experimental compositor backend atm always uses DRM_FORMAT_MOD_INVALID, i.e. implicit modifiers, even if not advertized by the compositor. And I guess implicit modifiers don't work on Vulkan.