I just tried out Discord, when Skype wasn’t working properly.
The new Linux client ( 0.0.4 ) works really well.
Still just a proprietary app though, right?
The CoTech instance of NextCloud run by @Chris has a Talk app that I’ve not used yet but apparently works well 
Have you tried out Mumble? I’ve not, but similar to Discord as far as I can tell, but open source.