Prosody or Snikket. But I develop both so might be biased 🙃
Happy to answer any questions though.
@Twelve Both Prosody and ejabberd (and others such as Tigase, Openfire) are generally up to date with modern XMPP protocol requirements, so you don't have anything to worry about there.
People tend to prefer one or another due to things like: ease of setup, resource usage, scalability, possibilities for customization.
@Twelve Prosody has a focus on being lightweight and very flexible. It has a plugin-based architecture so is *extremely* customizable (we have an active community and over 350 community modules at https://modules.prosody.im/ !). One of the main complaints people have about Prosody is that some important functionality is still in community modules and not bundled with Prosody out of the box, but we're working on that. A good setup guide is: https://homebrewserver.club/configuring-a-modern-xmpp-server.html
@Twelve ejabberd... bear in mind I haven't used it for a long time. It had many issues when I used it about 12 years ago, but has improved a lot by all I've heard. It also has many built-in options for scaling (e.g. if you want to run a cluster of multiple servers for load balancing) that Prosody doesn't have.
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