Not to bring life to a dead thread, but in case someone has run into this issue... I just wanted to note my fix for this:
Most of the "this is not supported in your browser" messages generated by corporate/enterprise targeted web applications are in relation to the user agent string presented by chrome or firefox. I just add "Chrome UA Spoofer" to my plugins in chromium. Then I set the useragent to the relevant "linux" version of the install. This tells the server, just pretend I'm coming from a supported linux in xorg host and quit complaining that my useragent says "FreeBSD"
My current useragent as follows:
Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/61.0.3163.79 Safari/537.36
This works for everything I use on a regular basis for enterprise web apps... except for sadly google earth. Notable applications that this has alleviated most of my frustrations with:
Webex Teams (Previously Cisco Spark)
Webex Meetings
Microsoft Office 365 Web Applications
Hotmail (live.com/outlook.com)
Sharepoint
Citrix Portal
Zoom Video
Gotomeeting
Also, specific to webex, I believe there is a Webex plugin for Chrome in the "Chrome Web Store"