There are a number of Science fantasy settings. I grew up with He-Man, Thundercats, and Krull so thats my default vibe.
There are the Barsoom Clones (BX Mars, Warriors of the Red Planet)
Operation Unfathomable and Anomalous Subsurface Environment for Labyrinth Lord,
Carcosa for LotFP, and Gathox Vertical Slum by the Hydra Cooperative.
Troika and some of the above lean closer to what Id call Acid Fantasy, the kind of setting that goes on psychedelic rock album covers.
Id like a setting with Gamma World fused with D&D. Mutant Future had a few pages at the end to discuss the unholy fusion with labyrinth lord they call Mazes and Mutants but they didnt give it much space to breathe. Mostly advice on keeping the rules consistent.
What are some Ive missed? What would you like to see in a science fantasy game?