SimpleX has the best privacy, because of removing metadata.
Signal comes close, and has many more users. Probably some of your friends already use it.
If you want something similar to Telegram/Discord/Slack, then Element (Matrix) is what you’re looking for.
All of the above are E2EE.
Apps that don’t work:
As far that I know, that’s it.
Try https://simplex.chat. Better privacy and no phone number required.
Most cryptocurrency communities use Discord or Telegram. It’s such an embarrasment.
If you need a Chromium derivative, then Brave is probably the best choice. It’s open-source, and includes ad blocking. Just don’t use its crypto token.
I prefer Firefox over Brave, but sometimes I might need a Chromium derivative for a particular site.
And a service like SimpleLogin for having a different email address per service.
And unless you’re using a social network site and you want your followers from other social network to find you there, use a different username too.