IMhO, one company tacled that very problem head on and did a fantastic job and it's my by far prefered chat (+ more) app today. Ironically, that company, https://keybase.io, got acquired by Zoom. Keybase still works today (thankfully), but there are AFAIK no guarantees for how long.

Keybase Chat is fully encrypted, persistent, and cross platform, and has the best solution to the identity problem.