Dunno if I go actively searching for difficult music, so I may not have the best answer for that specifically, but here are 5 albums I consider hidden gems or underappreciated:

Horse Bitch - RIP Pistachio

Tattle Tale - Sew True

Gaytheist - The Mustache Stays

Codefendants - This Is Crime Wave

Irist - Gloria (actually an EP, if you'll allow it).

These probably won't take you 5+ listens to appreciate, but I do think they're smaller releases worthy of greater attention. Hopefully that's close enough for you. ✌️