https://movim.eu/

It's based on XMPP, which means it's open-source, federated, and has E2EE in private chats. It also supports video calls, including in groups (which most other Discord alternatives have problems with).

Also, there's no phone number or even email requirement to sign up. You can set a recovery email, but you can skip that step during setup. Just pick a server, username, and password

The main thing it's missing right now is "places" aka what Discord calls servers/guilds. But they're currently working to roll that feature out soon

https://slrpnk.net/post/34490207

haven't gotten around to trying it myself. But the fact that it's built on XMPP is cool, and I hate that that all these new clients seem to develop their own new standards rather than build off what already exists.

Sounds like movim as a project has been around for a while, but recently moved to be more discord like in intention, so it's picked up interest there.