You might like Space Trader:

https://memalign.github.io/m/spacetrader/index.html

If you like replaying to explore all the narrative outcomes then Slay the Princess, though it has less mechanical depth and a very different tone.

Try "Urquan masters"

There's a direct sequel to this game called Beyond the Chiron Gate. I enjoy it less than Seedship, but it is more complex for sure.

Long time ago I found this game https://echa.itch.io/50-years-alpha

Similar as in also a space setting or just text adventure game?

There's Warsim which has an incredible amount of depth but with a medival fantasy setting instead.

Or I Was a Teenage Exocolonist