Nope, just Matrix. Second best option is XMPP with various cobbled together XEPs but that has its own set of problems.

For all the (sometimes rightful) grief Matrix gets, it's essentially the only solution targeting hard problems like multi-device encrypted group chats[0] or truly federated multi-user chats. It can also be a very quickly moving ecosystem, which is difficult to handle when you're an open federated spec. Hence why several of the complaints in this post are caused by old and no longer supported clients and servers.

[0] Infamously, WhatsApp and LINE both support encrypted chats but all the encryption keys are stored on your phone, so you can only have one phone working at a time and desktop access is actually routed through it.

> and desktop access is actually routed through it

I think this is not true anymore. I’ve had it working with while my phone was off.