Some of my close friends and I have been using deltachat. It works off of email (has encryption) but looks like a chat program. No centralized server as it uses each individuals email server, they would have to take down all the mail servers . Works with gmail just fine, private domains are better but almost any email address will work. Nothing is totally private if it goes out on the wire. I don't know how email servers would handle this on a large scale but we've been using it on a small scale for a year and love it.

Could never get on the damn platform anyway, so no great loss.

Do you run or help admin a big telegram channel? Even if you don't, it's time to start thinking about second and third backup plans to communicate with your group when the censorship start coming - Nothing is safe at this point, so a Signal group, Discord group, IRC - whatever it may be, ensure you can communicate with those you've hung out with the last 2 years.