John Carter of Mars by Edgar Rice Burroughs is an open IP, at least for the first several books.
Leveraging all the underlying work for Conan Exiles, it might be worth the effort to make a Barsoom Exiles game set on Mars, of course. Except for art assets, it could almost be the same game. Exceptions to this would be rifles or other projectile or ray-type weapons, and the flying craft, which could certainly be limited to altitude and speed. The flying craft might be an adequate replacement to teleporting, slower than instant, but faster than running on foot by ~2x. Even without either of those additions, it would still be a great experience.
Otherwise, the world of Barsoom is full of many different biomes, ruins, cities, races, creatures, and monsters.
I suggest this because, simply, I would love to play and role-play in such a world.
P.S. The John Carter Movie was pretty decent IMO, but there is an entire book written about how this movie was wanted for so long, and then when it was made, the marketing was utterly flubbed. “John Carter and the Gods of Hollywood”
A review of the book by a fan of the movie:
Instant find search string: “geeksofdoom, gods of hollywood”