On Android, I'd just use Newpipe[0] which I absolutely loved; they kept up with Youtube's breaking changes (usually a day-of debug build until the fix reached the main release), and it was such a nice and out of the way music player with everything you could want. (Adhoc playlists, great functionality for queue next/queue, really intuitive UI, backgrounding, etc)
On iOS, I wasn't really able to find an equivalent besides side-loading modified Youtube.app clients to enable the basic features I'd want (all of which are locked behind premium normally). Even with the premium features unlocked, the Youtube app really doesn't behave like an iOS app should, and it's significantly worse than Newpipe in my opinion.
So I'm just curious what about Premium is worth it for you and what it brings that justifies being a subscription. If the answer is just "it's the only option", I get it, can't really argue with that, but really hoping there's something I'm missing that makes Youtube Premium more palatable.