Not really sure besides music blogs when they show artists who have submitted music to them. I believe Pigeons and Planes does that. I don't know what kind of music genres your into but I know of an underrated Hip Hop artist. I'll leave you the link not sure if you'll like him but that's all I got.
Doesn't seem there's a direct answer (afaik), best bet imo is to just go down rabbit holes of "Fans also like" section within Spotify, starting from the most niche artist or song you enjoy - all depends on your genre preferences really.
It's easy with metal haha, i had the group/album "Colma" recommended to me today by the app and then found Vaner Versori from there... just had to share because i don't think i've ever seen zero monthly listeners before