Finding good Indigo Park stuff feels like hunting for a very specific mood lately. I keep bouncing between Archive of Our Own and FanFiction.net, but AO3 wins for me—the tagging system means you can actually filter for the creepy, atmospheric stuff that fits the game’s vibe, not just generic horror. Tumblr’s a mess for full stories but amazing for snippets and headcanons that inspire writers; I found one author there who crossposts to AO3, and their stuff nails the liminal space dread.
That said, I’ve seen some surprisingly tight, character-focused pieces on Wattpad too, buried under miles of less polished work. You really have to dig, though. My take is to start on AO3 with tags like ‘Indigo Park (Roblox)’ and ‘Rambley Robinson’, then check the authors’ profiles to see if they link to other sites they use.