Instant Messaging: It's not about the app - #XMPP provides sovereignty of your communication
Read a comment in this blog post:
https://xmpp.org/2021/01/instant-messaging-its-not-about-the-app/
@xmpp@fosstodon.org What are good XMPP servers anyway that I can run with own reverse proxy?
You can take a look at the resources in the Getting Started section at xmpp.org: https://xmpp.org/getting-started/