[olig15]

I use this, which uses crowd sourced thumbnails from within the video https://dearrow.ajay.app works really well. Made by the dev that made SponsorBlock

[jacekm]

I use https://addons.mozilla.org/en-US/firefox/addon/clickbait-rem... - it replaces thumbnail with a frame from the video.

[franzb]

A dumb thumbnail is a useful signal to know that I won’t want to watch the video anyway :)