I use an app called Seal. You could think of it as a fronted for youtubedl. The interface is really beautiful and you can download videos from many different websites.
Another one is ViMusic, this is just an app that streams songs from YouTube music without any ads.
edit: fixed spelling of vimusic
Just in case, NewPipe is a super complete YouTube player without ads (and there is a fork also without sponsor sections). It can also view comments of the videos and it can keep your own subscribed videos feed, all without using a YouTube account. You can also download them, and play the audio only, also in the background. All in all, my complete YouTube replacement.