There is also matrix and nextcloud has the talk integration (also based on the fediverse Afair)

Have not implemented it but would recommend Jitsi or big blue button. If you want to have a discord experience maybe also revolt chat

Skype for business? /s

Mirotalk might be an option:

https://github.com/miroslavpejic85/mirotalk

Federated Computer offers hosted Jitsi and Element/Matrix (and a ton more) at https://www.federated.computer for $39/month/domain. Maybe that’s a fit for you?

zulip/jitsi