I have just tried playing the 12th song from “Italy Top Songs 2021…” and 4th song from “Legismertebb…”. They play well.
I am wondering if there’s a bug in Curl on Debian Buster that somehow handled the audio URL wrongly and sent an invalid request to YouTube (which would of course reject it).
If you can, could you try using the MPD I have here ? Follow the instructions there to activate it and see if the error persists. This MPD is the one I am using on my Volumio 2.853.
I am unable to try Volumio 3.015 at the moment but I will do that when I have time.
-Patrick