Some companies are reducing their development costs by only testing in the very most popular browsers (for example, Chrome on Windows and Android, Safari on Mac and iOS) and telling people to use those. This is bad for user choice, obviously. In some cases, you may choose to vote with your dollars and change services. But in other cases, you might need to use their preferred browser for their site or find another workaround. But sometimes "unsupported" indicates that one of their scripts didn't run as expected, and it's actually due to content blocking. You can try to fix sites by turning off some blockers, as follows: (A) For Firefox's Tracking Protection feature, the shield icon toward the left end of the address bar usually turns a bit purplish when content is blocked. Click the icon to learn more or make an exception. See: [[Enhanced Tracking Protection in Firefox for desktop]]. (B) Extensions such as Adblock Plus, Blur, Disconnect, DuckDuckGo Privacy Essentials, Ghostery, NoScript, Privacy Badger, uBlock Origin or uMatrix usually provide a toolbar button to manage blocked content in a page. There may or may not be a number on the icon indicating the number of blocked items; you sometimes need to click the button to see what's going on and test whether you need to make an exception for this site.