Piped and Invidious.

I prefer Invidious for vague reasons, though either it or the instance I use most often seems to fail about 25--50% of the time on videos, with more popular content (e.g., music) failing most often, so I'll fall back to Piped.

Otherwise I use mpv / ytdl, and in fact greatly prefer that approach.

For those prefering a standalone GUI, there's VLC.