Everything works if you use User-Agent switcher extension. So they went through the trouble of making an "unsupported" page and redirecting you to that page instead of doing nothing
there is a good reason that most of the people prefer apple for its simplicity, its because apple only shows you what is required. i agree with you there.
Extremely frustrating. If a user is smart enough to use Firefox, they're probably also smart enough to open another browser if a site does not happen to work on Firefox. (Which I haven't experienced for a while, except when using ESPHome which requires WebSerial)