I got distracted from my work so I made some Continuwuity propaganda. Continuwuity is a lightweights Matrix chat server that you can self-host pretty easily. Give it a try :3
overall we need something to text
pretty much Matrix's entire point
(plus send files)
also implemented in pretty much every server and client; I think even Element can send files
call
look into e.g. #matrixrtc:continuwuity.org — sable requires a setting to show the call button in non-DM rooms
video/screen share
unfortunately this is the only thing I'm not confident is supported
bonus for emojis, stickers
should be available with any im.ponies-compatible client such as sable