I am wondering why I haven’t found GNU Jami messenging and conferencing (developed by savoirfairelinux) even mentioned in the forum.
It has clients for all major platforms.
Even has an LDAP capable organizational client configuration management-server package, see: https://jami.biz/jams-user-guide
Looks like this is a solution that is precisely made for self-hosting.
Jami is mostly peer-to-peer (“Swarms” are coming also) so using our yunohost server “coturn” for peer discovery and notification could be doable. It’s beyond my skills though, but Jami is a great app/service that in my experience lacked good notification in systems without google services.
Once connection was made it works superb for both video and chat.