I see you are man of culture to have read Legendary mechanic too.
I have mansion in post apocalyptic world is great, but the mc got harem and pretty much h*rny as downside.
Supremacy games is great it is mixed with superpower tho and human here pretty much being underdog, there is a tempest of stellar war for pure sci-fi which is good enough as well a mech touch, beware mech touch is pretty heavy novel to read with very long dialogue and description format.
I also can reccomend another 2 that have spaceship with many variety civilization in space but sadly got mixed with cultivation too, they would be Star odyssey and forty millenium of cultivation, both Chinese but for latter they will go through certain amount of time on home planet first before embarking on interstellar journey.
