Same issues I have, (s23 Ultra), but in my case video missing frames after i use pause button and start playing again. For me one way to get rid of it was changing quality from 1080p to 720p and again to 1080p. Your solution to double tap for 10s jump works for me either. I believe it is a YouTube problem cause same thing happening on Firefox Nightly for developers In addition YouTube tends to enforce lower quality playback even when addon for enforcing certain quality is set to another value. Next thing I have checked was uBlock Origin and after disable it nothing in this matter changed so it is irrelevant.

I also have noticed this recently after an update on my S10. I have found that any video played through firefox from any source is choppy with low frames unless you use the progress bar to skip or replay which then makes playback smooth. Refreshing the page Makes videos choppy again regardless of whether you get playback smooth or not.

Encountering the exact same issue on my S20 FE

Same problem here. Samsung S10+. All video sources, not just Youtube. Turning off uBlock does not help. Checked chrome and it does not have this problems. Not sure when this started, but at least 3 months ago. Probably after latest Android update.