Yes YouTube Premium will play with the screen off (using the app. No idea about using a browser).

cuu508 3 days ago | parent | next [-]

In a browser, it works even without Youtube Premium :-)

Firefox mobile, m.youtube.com, "Video Background Play Fix" browser extension.

	▲	fdgjgbdfhgb 3 days ago \| parent [-]
		Works for me without an extension, you just need to click play again after leaving the YouTube tab/locking the phone

tcfhgj 3 days ago | parent | prev [-]

So does ReVanced YouTube