I wouldnt say its white supremacists but rather cacs who have little to no real contact with Black folks and therefore, are more likely to be white supremacists.
I look at reddit, mass shooters (the illinois mass shooter for example), certain rabbit holes of YouTube (for example this channel called Dumbsville and the uploader is very much a cac suburbanite who is obsessed with Soundcloud/Hipster Trap rap) as proof. And its a lotta white kids who dont have any explicit solidarity with Black people but LOVE hip hop.
It kinda makes sense....Hip hop for white kids of the 2020s has become what punk, emo, and heavy metal was to white kids in the 90s and 2000s. Simple as that.
If you notice, these cacs are basically the evolution of hipsters and like a certain type of rapper who tend to be synonymous with soundcloud, genre bending and high fashion, arent super duper lyrical, and arent extremely regional hood rappers (so no Detroit, Memphis or LA rappers). Off the top of my head, I can cite Ye, Uzi, Carti, Tyler the Creator, Cudi, Travis Scott, Thug and YSL, XXXTentacion, Lil Peep, old Chief Keef, as the main guys who fit this mold.