https://gs.statcounter.com/browser-market-share/desktop/worl... 5.59% for Firefox in the desktop category. (mobile is tough for any alternative browser - chrome has a hard time on iOS although I'm sure only being a skin over webkit doesn't help)

Desktop is a better market to compare anyway, if including Edge. Is Microsoft even trying anymore on mobile?

I think a lot of University computer labs still use Firefox. At least at some point, that was because it was easier to lock down — no directory "an administrator" (i.e. malware) could just dump an extension into to treat it as force-installed.