The web version of Skype works fine in Linux. Also, there is https://meet.jit.si/ - This works very well in WebRTC capable browsers.
Full disclaimer: I'm a friend of the founder, however I'm a paying customer due to the fact that
1. It's worked wonders with my clients and 2. It's so much better than hangouts or skype.
Compared to the big boys it may be considered a bit spartan but for what it does, it does it extraordinarily well.