i'll second that Watch the Roots rec, it's GREAT

Detective Pony (https://archiveofourown.org/works/2427119/chapters/5371283) and The Serendipity Gospels (https://archiveofourown.org/works/335176/chapters/541856) are fandom classics but i'll rec them here anyway

i also really love Vinbre the Novel (https://archiveofourown.org/works/31830013/chapters/78803398) bc its worldbuilding and characters are incredible!!

and Modern Cannibals (https://archiveofourown.org/works/10619448/chapters/23486718) is less a Homestuck Fic and more a Fic About Homestuck but it's REAL good and heartwrenching. it is a Very heavy read however and that T rating is misleading, it's much closer to M.