I noticed that some modern (badly coded) pages needs quite big resolutions and 100% zoom settings of Firefox does not match to Pinephone screen.

Pinephone
zoom fullscreen viewport resolution
100% 960x480
90% 1056x528
80% 1200x600
67% 1440x720 = real Pinephone resolution
50% 1920x960

Notice that 67% zoom without full-screen viewport is only 1440x537 and some pages needs at least 800x600 to proper use.