I'm using beeper - and it really lowers the mental overhead of tracking messages for me - I have some people on signal, some on messenger, some on sms, some use dms on discord.
It's great to have a single app that shows notifications and tracks conversations.
Much better than having to try and remember if my conversation with "Tom" was via sms or signal or something else; he might have a messenger account but not use the app - doesn't matter - I just open beeper and find the last conversation and continue from there.
Ed: I don't use beeper or messaging on desktop - so Franz is DOA for me.
Which is a shame - it looks like a solid product.