I have a pinephone and try it out year after year.. Well, let's just say that there is so many areas of improvement to make "GNU/linux" run on a mobile device (that sorta includes laptops as well, even though I have done so for years) that we might as well start over from statch.
For example one can't just let everything run whenever it wants, wasting battery life. Android's "more complicated" system and binder was criticized in this thread, but that's exactly what ties together the whole thing to be able to run on a device that fits in your hand, with centrally managed "let's pause this app now" etc
There are more, not every application that works fine has metadata filled up (and not everything is on Flathub either).
I do use some webapps, but with Epiphany rather than Firefox.
See also: https://linuxphoneapps.org/