It is good to read these comments. I am also looking for somewhere else to go. I do not like what fb is doing either. I have been reading some on these othe websites and as for me, i think i will try Mastodon. I like the things i have read about it. Good luck to everyone that is deciding to go somewhere else. Because it isn’t right that fb is trying to control everybody.
A simple chat (slack style) it's enough. Just having the possibility to send messages either single user or team (#channel). But please don't forgive to give an useful appeal to mobile app (worst error of competitors is, have a good app but totally no mobile friendly!) i would expect to have a similar whatsapp or slack app for messaging within the slack mobile app!