>>mig4ng+(OP)
Personally, I can't stand how distracting YouTube thumbnails are. I found this list to block them from the sidebar when watching videos.
! Hide all of the recommended videos on the right side of the page, except for the first up-next video.
! If you have a tall monitor you may need to add more entries, this blocks the initial list on most resolutions.
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(2)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(3)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(4)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(5)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(6)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(7)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(8)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(9)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(10)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(11)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(12)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(13)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(14)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(15)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(16)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(17)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(18)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(19)
www.youtube.com###items > .ytd-watch-next-secondary-results-renderer.style-scope:nth-of-type(20)
! Prevents the list of recommendations from expanding when scrolling down.
www.youtube.com##ytd-continuation-item-renderer.ytd-watch-next-secondary-results-renderer.style-scope
www.youtube.com###continuations > .ytd-watch-next-secondary-results-renderer.style-scope
www.youtube.com##.use-ellipsis.ytd-watch-next-secondary-results-renderer.style-scope
www.youtube.com##ytd-compact-playlist-renderer.ytd-watch-next-secondary-results-renderer.style-scope
Also, if you hate Shorts as much as I do, use this to hide them from appearing in search results.
youtube.com##ytd-rich-section-renderer:has(#rich-shelf-header:has-text(Shorts))
youtube.com##ytd-reel-shelf-renderer:has(.ytd-reel-shelf-renderer:has-text(Shorts))