No ads (except the ones that are actually part of the video), download videos, and no tracking.
Desktop:
Freetube ( https://github.com/FreeTubeApp/FreeTube/releases ) on Windows/Mac.
Mobile:
NewPipe ( https://newpipe.net#download ) if you have Android, which a lot of you don't have. You're stuck with the shitty Apple apps.
It even lets you stream audio only (like free Youtube Music subscription, which is gay that anyone would pay for Youtube anyway). Can iOS even play music in the background? I think it's a new feature for them.
EDIT: added NewPipe link. You can't download NP from the Google Play Store. You can also install it through F-Droid.