Gazetteer is a pretty fun time! It reminds me of collaborative map-making games like The Quiet Year or Companions' Tale, but GMful and directed. As the GM, you come to the table (or social media platform of your choice) with a map already drawn and seeded with interesting symbols, but with limited expectations about what it all really means. Then, you ask guiding questions. The result is a small, ready-to-game adventure locale that may go in directions you would not have considered if writing in a vacuum!
I have completed one locale in the game's dedicated Facebook group, and started a second. My first ended up super flavorful, and I was very happy with the final gazetteer writeup that I made for it. If I have any complaint, it is with forum games in general -- precisely where you play matters a great deal. You need buy-in from your community, or else a post can languish for days (or indefinitely). Be prepared for that, or aim to cultivate a playspace where you can be fairly certain to see a game through.