Libretube and some Piped frontends are currently down as Google is reportedly "rate limiting" (aka IP banning) these instances according to the Piped Matrix group. A workaround is being implemented, but if you are on Android and are in desperate need of Youtube audio during work like me Newpipe is still running.
its because compared to other (older) solutions, it's a pain. you gotta download the APK of the manager, then it's asking you to root your phone or give it an APK of the app you're trying to crack, so I guess I gotta go hunt for a YouTube APK?
too much work when I can just stop watching YouTube, and for the one video per week that's unavoidable, make do with my half-brokem version of YouTube Vanced that's still on my phone.