It’s the other way around here, I know very little Alfvén (no piano) but I like Stenhammar - a little bit at least. His is also the most Swedish sounding music of the classical composers I know. It captures a bit of the language, a bit of the nature, and a bit of the national character.
Maybe Samuel Coleridge Taylor? I’ve known about him for years but never explored his music.
Edit: I didn’t see the precision about folk elements. Maybe Percy Grainger for the Poms (country gardens etc), but he was Australian.