On android I use Revanced. It patches the official Youtube app (patches are open source) to greatly expand the base functionality and offer a lot more customization of the UI.
For me the best features are ad block, sponsorblock (skips in video sponsored segments), and complete excision of shorts from all aspects of the app.
It also works on Youtube Music, effectively allowing free premium (just don't get the local downloads of your most listened tracks to help save data, but I have unlimited anyway).