Curious whether you've tried with the new (non-PPA) repo directly from Mozilla as of v122 [1]. I think the old PPA was also Mozilla, so I don't know what may have changed aside from being more publicly acknowledged. Might be worth a try?

I don't have an Ubuntu VM at-hand but on Debian bookworm it installed fine, and (after tweaking one line in profiles.ini to point to my old ESR profile) it loaded and played Widevine-protected videos without any issues.

[1]: https://support.mozilla.org/en-US/kb/install-firefox-linux#w...