I haven’t seen anyone mention Endless Sky.

It’s in ongoing development, but there are many hours of content. You fly your ship around, you can be a trader selling goods between planets, be a pirate attacking other ships, or fight pirates and sell their stuff. There are lots of other quests, including a major and lengthy story line quest series and other minor side quests with multiple linked parts.

There’s also an unofficial port to Android available on F-Droid here.