https://delta.chat/

https://delta.chat/en/help#e2ee

I gave it another try last week

• the onboarding automatically creates a username/password on the server you selected, more details here: https://chaos.social/@delta/115479392746850836
• E2EE using openpgp
• fast and light on resources

It's still in development, it's not a fully fledged replacement for Matrix yet, but I could see it replace Signal at some point.

For a list of servers: https://chatmail.at/relays