Have you looked at the Expanse RPG? I thought that it was a good balance: a bit of hard sci fi, but workable mechanics. For more technically minded groups you can dig harder into the science, but you can hand wave some of the space travel rules if that is not your jam without breaking the game.
I played the game with engineers in the group, but I'm the type of GM that is happy to have players do some of the rules heavy lifting. I was less intimidated about the space-travel mechanics in The Expanse RPG than the lore.
I like The Expanse RPG as a game system, but I prefer systems that don't have a lot of lore from wildly popular books, TV shows, and movies.
Also, I personally find more hard-science or reality-bound RPGs less satisfying than fantasy. Space fantasy is more fun for me to play than more reality-grounded systems.