The app isn't in any app store(officially) it's only hosted on their own site/GitHub. If you are root you can take advantage of a lot of nice to haves that a non-root install misses(such as the "open in app" function of Firefox)
Oh! Ty. I remember reading about it but it seemed a bit daunting and I never got around to really doing it. I will have to look into it again. YT is so miserable on the phone and the obligatory settings absolutely wreck my battery.
It's really not that bad. All you need is a YouTube apk of the recommended version and the revanced manager. Finding the correct YouTube apk can be a bit annoying but the patching process is completely automatic.