[bityard]

In my case: several financial institutions that I have accounts with and lots of enterprise apps and gear with web UIs either break silently, have certain functions that don't work, or block with an error telling you to use a supported browser. (If they're nice, they even tell you which ones are supported.)

For a while, Slack didn't support all features on Firefox despite the technology being there, I don't know if this is still the case.

[smarnach]

Please report this kind of bug on webcompat.com. It's often possible to get them fixed.