Oddbean new post about login | logout mind sharing the list? Sounds like a well thought out resource Element/matrix Signal Nostr Are my go tos
I've been looking at Session too, no phone number or email required. And xmpp works well, both for text and calls. I use Cheogram app on my android for that.
Session is decent.
How many relays can they really be running? Pretty sure oxen is the only group running any. Their financial model depended strictly on a token to incentivize people to run nodes and I feel like that went nowhere. Also, while they once had Signal forward secrecy, they quit using it for some reason. Dunno why. So messages *could be decrypted if they run a mitm attack and end up getting access to the keys. Its just kinda weird. Probably fine for low threat models but I'd stick with OTR or OMEMO over XMPP or Simplex if you're concerned about targeted surveillance.
If your ssh public key is published somewhere accessible, it enables someone to spin up an OpenBSD VPS, add your key to the approved keys list, get you the ip, and you can all ssh in and use the internal mail to talk back and forth. With the files never leaving the server. A tool for more serious times.