Optimal, no mobile number or email required, works over TOR
CONS:
They monetize with a token (altcoin) by the name OXEN, it is their own network and the nodes of the privacy token carry the data end to end encrypted, the liquidity is poor and therefore a potential 51% attack is plausible, although not likely.
Optimal voice/video quality, no mobile or email required, novelty app, decentralized
CONS:
A battery killer, during configuration, to avoid killing your mobile battery set the notification to work only when the application is open. This setting will render the application useless for receiving urgent messages or calls, you will need to agree with the other party to use the app. It is quite new, here an article I wrote recently about it4
Maybe briar, they don't require phone number, not even email, just login and password, and I like that you can chat within a local network without internet acces, although I don't remember if it has calls.
Have you looked at SimpleX Chat? Totally private and decentralized (the infrastructure is similar to nostr), no user IDs of any kind, including no phone numbers. SN even has a chat that you can talk to them on. It's a really good option that I'm sure many people around here would endorse.
I still use Signal in some cases, just because SimpleX doesn't feel quite polished enough for my family and friends to get into it yet, but it is definitely a project to look into friend
Footnotes