I had a Fold4 and now have an s25 Ultra and had none of those issues with Firefox either. Works just fine for me and I even have some extensions I’ve put on that aren’t technically supposed to work in the mobile browser so I was fully expecting some jank. But still works fine.

I had a folding phone (Fold4). Once a video was playing the fold wasn’t as noticeable as long as you looked at it straight on. From an angle, the fold was annoying.

The worst part about the phone was that it was uncomfortable to hold when folded or not, it was cumbersome, and finding a good case for it was nearly impossible.

I would rather carry something like my Deck in a case than save a little space with a folding device. Those folding screens are also very shiny and super sensitive. You can scratch those screens with your finger nails.