A lot of the reported issues with YouTube on Firefox (especially when paired with adblockers) involve things like increased page load times, UI elements not functioning as smoothly, or even video playback glitches. Some of this is due to JavaScript that’s intentionally designed to slow things down if you’re blocking ads or using a non-Google browser, as we’ve been discussing.
IIRC the story was, when Youtube was redesigned a while ago they used an early spec for Web Components, that they were pushing to be standardized and was fully implemented in Chrome. But they had to add Polymer as a polyfill for other browsers. Then the version of Web Components we actually got wasn't entirely compatible with that early spec, so Polymer is still in use for non-Chrome browsers.
I don't know how much of that's changed since then, but the complaints are basically the same as when that happened.
I haven't seen any bugs on Firefox mobile + uBlock Origin + Android + Pixel 4a 5g (I hate upgrading phones, sue me).
The only glitch I reliably get is watching videos at 1.5x sometimes freezes video (but audio still plays). Expect that's more hardware and memory pressure related tho.
Also, I wasn't aware YouTube mobile has ads? I think uBlock might be eating them. Although possibly whatever is lagging others experiences too...
