There is a third party youtube app which supports that.YouTube music must be the most useless music streaming service for free users. They don't support a basic feature like background play, which is available for free on every single music streaming service.
![Lol :lol: :lol:](/community/data/assets/smilies/lol.gif)
![Lol :lol: :lol:](/community/data/assets/smilies/lol.gif)