I seem unable to fix this. I have tried ./mach bootstrap and it seems to think zstandard is present. I have pip3 install'd zstandard and still it seems to fail. There's a hint below that you can run with --disable-bootstrap but commands I've tried seem not to accept this.

0:05.38 Updating bootstrapped toolchain in /home/lhansen/.mozbuild/pkgconf
 0:06.55 Setting up artifact pkgconf.tar.zst
 0:06.55 Using artifact from local cache: /home/lhansen/.mozbuild/toolchains/5857ea71e85403be-pkgconf.tar.zst
 0:08.01 Error running mach:
 0:08.01     ['--log-no-times', 'artifact', 'toolchain', '--from-task', 'I4gIyNT_SLas0D1ogMkyCA:public/build/pkgconf.tar.zst']
 0:08.01 The error occurred in code that was called by the mach command. This is either
 0:08.01 a bug in the called code itself or in the way that mach is calling it.
 0:08.02 You can invoke |./mach busted| to check if this issue is already on file. If it
 0:08.02 isn't, please use |./mach busted file artifact| to report it. If |./mach busted| is
 0:08.02 misbehaving, you can also inspect the dependencies of bug 1543241.
 0:08.02 If filing a bug, please include the full output of mach, including this error
 0:08.02 message.
 0:08.02 The details of the failure are as follows:
 0:08.02 ModuleNotFoundError: No module named 'zstandard'
 0:08.02   File "/home/lhansen/m-u/python/mozbuild/mozbuild/artifact_commands.py", line 576, in artifact_toolchain
 0:08.02     unpack_file(local)
 0:08.02   File "/home/lhansen/m-u/python/mozbuild/mozbuild/action/tooltool.py", line 993, in unpack_file
 0:08.02     import zstandard
 0:08.02 Sentry event ID: 238432ac4f244dfbaf7b7a770df72fe5
 0:08.12 Sentry is attempting to send 0 pending error messages
 0:08.12 Waiting up to 2 seconds
 0:08.12 Press Ctrl-C to quit
 0:08.43 ERROR: Command '['/home/lhansen/m-u/obj-reldebug/_virtualenvs/build/bin/python', '/home/lhansen/m-u/mach', '--log-no-times', 'artifact', 'toolchain', '--from-task', 'I4gIyNT_SLas0D1ogMkyCA:public/build/pkgconf.tar.zst']' returned non-zero exit status 1.
 0:08.43 ERROR: If you can't fix the above, retry with --disable-bootstrap.
Error running mach:

    ['build']

The error occurred in code that was called by the mach command. This is either
a bug in the called code itself or in the way that mach is calling it.
You can invoke |./mach busted| to check if this issue is already on file. If it
isn't, please use |./mach busted file build| to report it. If |./mach busted| is
misbehaving, you can also inspect the dependencies of bug 1543241.

If filing a bug, please include the full output of mach, including this error
message.

The details of the failure are as follows:

Exception: Process executed with non-0 exit code 1: ['/home/lhansen/m-u/obj-reldebug/_virtualenvs/build/bin/python', '/home/lhansen/m-u/configure.py']

  File "/home/lhansen/m-u/python/mozbuild/mozbuild/build_commands.py", line 220, in build
    return driver.build(
  File "/home/lhansen/m-u/python/mozbuild/mozbuild/controller/building.py", line 1296, in build
    config_rc = self.configure(
  File "/home/lhansen/m-u/python/mozbuild/mozbuild/controller/building.py", line 1677, in configure
    status = self._run_command_in_objdir(
  File "/home/lhansen/m-u/python/mozbuild/mozbuild/base.py", line 842, in _run_command_in_objdir
    return self.run_process(cwd=self.topobjdir, **args)
  File "/home/lhansen/m-u/python/mach/mach/mixin/process.py", line 183, in run_process
    raise Exception(

Sentry event ID: b0da98b503034b249dbc2fd52ad4ecff
Sentry is attempting to send 0 pending error messages
Waiting up to 2 seconds
Press Ctrl-C to quit