I don't think it has anything to do with what GPU you have. Cycles shaders are white if you enable hardware shading in the previews, and it will display whatever you've got for Firefly if you disable it (which might lead you to think you're seeing Cycles previews, but you aren't). I treated myself to a 4090 so it's not like my GPU is not up to par.

I know I could just toggle between firefly and superfly to get different previews, but 90% of the time when I do anything as a temporary thing (e.g. add some working lights), I forget to change back before hitting render. :)