Can we please stop making comments that are just complaints against Meta and Microsoft? Let's keep the discussion practical, centered around the solutions/workarounds.
I will repeat my current workaround: For me, the older version of the non-browser app is working great (downloadable from https://messenger.en.uptodown.com/windows/download/1026550438). Every time I reboot the PC and the app is loaded as part of that process, it suggests upgrading, but I simply click "Not Now" and the popup goes away. (I know that others have described how to make it a Chrome-based browser app, but I use Firefox, which Messenger doesn't yet support for video/audio calling.)