I also get this error. If you go to Hamburger - Help - More troubleshooting information, then it lists there recent crashes. If you click on the crash, it’ll show some details and matched bugs on Bugzilla.
Here is the bug report it matched: 1777927 - Crash in [@ XDisplayString]: Consider blocking vdpau_drv_video.so from being loaded
Based on the report, I went to ~/.mozilla/%your_profile%/prefs.js, and set media.ffmpeg.vaapi.enabled to false. The old profile works now.