Discourse 3.0 incoming

Since the update I’ve not been able to participateusing the latest version of Firefox and Waterfox. I get the following message banner at the top of the site:

Unfortunately, your browser is unsupported. Please switch to a supported browser to view rich content, log in and reply.

See screenshot below:

I get the same message at other forums that use Discourse >3 and it kinda sucks.