I sent everyone a message, roughly "hey I'm moving away from Meta products. From now on you can contact me through SMS or Signal." All the important ones followed me to Signal, not all, but enough. The rest are using SMS or calling, some have stopped contacting completely. Which is sad, sure. But I look at it as they don't think I'm important enough for them to spend 30 seconds installing Signal or using a SMS that is already available for them. So I assume they don't like me very much, which is fine. I don't think about them too much either.

That's the same issue everyone has/had, including me. You'd be surprised how alright it works to use SMS and phone calls once you get used to it. It's honestly refreshing. You don't have to go that far, necessarily, as there are other messaging services out there that I'm sure your circles find better than SMS.

Sure, you might miss out on some events and stuff due to others needing to remember that you're no longer on Meta platforms, but just be a little persistent and they'll remember to include you, just like they did me ;-)

I said the same thing then took the plunge a year or so ago. Now the people that I used to keep up with on FB text and interact directly with me more often even than FB and I enjoy it more.. Also don't have to incidentally see all the assholes in the process.

True, but someone has to start.

Just write them letters

All my friends and family know how to contact me because their my friends and family.

Nah, works fine. Sure, you won't get a nudge every 15 minutes but that's (surprisingly to some) totally okay. Just quit, there's other ways to keep contact with the people you care about.