the ones most of your contacts use, what's the point finding perfect messenger if nobody you know use it and you must move people over there and anyway keep installed other app for most of the contacts?

here you have chart comparison

https://www.messenger-matrix.de/messenger-matrix-en.html

and alternative

https://www.securemessagingapps.com

personally I like Element (Matrix) and Threema

edit: btw. signal best UX? do they finally show users how to force send unencrypted SMS or you still have figure it out with google? I remember their great UX when they were forcing PIN verification with nag screens taking half or whole screen, which was the last drop I moved with whole family away from that PoS, let alone how unreliable it was, whole network down because admin in US sleeping waiting hours until he fix it, their approach (aka hatred) to users reminds me Firefox devs, left Signal even before it became popular