itch.io

Hey! It's built off the chassis of Down We Go, plays with a simple d20 system with auto-hit combat, and shares similarities of gameplay with OSR (in the sense of lethality and gameplay around tactical choices to set yourself up for success vs running into combat for instance). It also has substantial narrative tools for players to build the world and environment they explore vs purely from the GM. Of course groups can lean into one or the other to fit their preferences.

I encourage you to pick up the Greenhorns Essentials version which is free/PWYW if you want to make sure it'll be a good fit. It has all of the rules and narrative tools so you can get the full feel of the game before diving into the full hardcover PDF experience.