A user on the VRC forum posted a few weeks ago that they had made (with AI) patches for Proton that lets VRC access camera.

They've published their custom build onto github, you can get the latest tar.gz release and unpack it into ~/.steam/steam/compatibilitytools.d/ (different for flatpak install, see the repo readme), then restart Steam, set it to run VRC with the new proton you just added, and tada :3