Endless Sky has a mobile port on F-Droid. You fly a ship around, doing trade, missions, attacking pirates (or being a pirate). There are also a few storyline missions, many hours of fun and the game is still in development. There are some quirks on mobile but I put many hours into it, it’s good fun.
Mindustry is also fun, and has many hours of potential. It’s also a port of a PC game, this one works very nicely on mobile. It’s sort of a Factorio (conveyor belts) tower defense game.