If you don't use Discord for voice much, Matrix has a pretty solid bridges you can use.
Hosting your own Matrix server is suprisingly way easier than I though - got a VM on hertzner for like 5$ a month, and there is an Ansible script that takes care of the setup for you. It's also one of those rare cases where someone made an Ansible script that actually works, instead of you getting stuck in dependency-hell (seriously, fuck npm. Not a single docker or ansible tool that has used it ever worked for me out of the box. Python can get simillarly annoying).
They have a pretty easy to follow guide, and the whole setup took me like 20 minutes. I only edited a few options in config.yml (mostly to add Messenger and Discord bridge), and ran the ansible, and it worked at first try.
So I could at least ditch both messenger and discord apps from my PC and phone, without having to convince anyone to quit their poison - with only issue being that you can't use Discord voice. And that the messenger bridge is still unreliable sometimes, but those are still minor inconviniences in comparison to my deep-seated hate for Meta.
Of course - Meta still gets my chat data and content, same as Discord. But at least they don't get anything else from my phone or PC.