Zulip looks interesting, will look into it
We've found matrix (with element or schildichat) to be rock solid though, honestly
Discussion
How is the node self-hosting story for Matrix these days? Is easy to get one running?
If you use a provisioning system, such as start 9 or cloudron, yes - very easy
If you would attempt a manual install, it would appear (given nostr:nprofile1qqs9pk20ctv9srrg9vr354p03v0rrgsqkpggh2u45va77zz4mu5p6ccpzemhxue69uhk2er9dchxummnw3ezumrpdejz7qgkwaehxw309a5xjum59ehx7um5wghxcctwvshszrnhwden5te0dehhxtnvdakz7qrxnfk experience) not straightforward
which is unsurprising given that matrix is an Enterprise solution, and this software category is rarely easy to self deploy (due to the wide range of server topologies it needs to support)