I can’t really tell you which one is the best, since I never used any of these (except for Session) for an extended period of time. Briar seems to be the best for anonymity, because it routes everything through the Tor network. SimpleX allows you to host your own node, which is pretty cool.
In the perfect world where you can convince your company to use anything other than MS Teams and that your family bothers to use anything that isn’t WhatsApp or Telegram. Unfortunately I don’t live on it 😭
Stay away from proprietary crap like Discord, Slack, WhatsApp and Facebook Messenger. There are enough FOSS alternatives out there:
In the perfect world where you can convince your company to use anything other than MS Teams and that your family bothers to use anything that isn’t WhatsApp or Telegram. Unfortunately I don’t live on it 😭