I'm on Windows 11 and only Normal 400 is working in Firefox 100 Stable, Firefox 101.0b3 Developer Edition, Tor 11.0.10 (FF 91.8.0esr), and Tor 11.0.11 (FF 91.9.0esr)
It does work in both Chrome and Edge, so I don't think it's a general OS issue
It does work in both Chrome and Edge, so I don't think it's a general OS issue
Firefox uses the Windows DirectWrite APIs. This means that Firefox leans into the support that Windows has for variable fonts, and that was dicey until a few releases ago.