if you go to something like https://beta.maps.apple.com/asd you bypass the browser check.

works on firefox, but it's a big sluggish.

It works for a second, then I get redirected to the unsupported page.

This doesn't work for Brave.

In my mobile Safari it doesn’t work either.

Edit: looks like iphone is not supported yet, https://support.apple.com/en-gb/120585

Agreed, but it was even more disappointing to also see the "unsupported browser" when I tried it in Safari.

That's downright ironic.