@thomas I cannot reproduce this in my Firefox; it's only scrollable downwards for me.
@thomas Oh, whoops, I misread your original post and missed that it's about *mobile* devices. I *can* reproduce it on Android Firefox. Let me see if I can get developer tools attached somehow...
@thomas So I couldn't get USB debugging working, but I *could* reproduce the issue in desktop Firefox by setting it to mobile emulation mode in devtools.
I'm honestly not sure what's causing this, I don't see anything that would obviously be the case. Removing the <main> element makes the overflow go away, but there's also nothing about the element itself that seems off?
My guess would be that there's some deeply-nested element somewhere that's relatively sized to the viewport (maybe 100%?) instead of to its parent, and that it's invisibly pushing out the 'boundary' of the page contents. But I haven't been able to find such an element yet.
@thomas Also, note that the 'overflow' tag refers to *any* overflow - including the (desirable) vertical overflow/scrollability :)