So it turns out when you deploy ships to a planet you don't earn they just set up home there and don't come back lol. But you can't recall them - so I have no idea how to colonise an unowned planet and now my Yamato is hanging out on one and I can't get it back.
▶️ DTube ▶️ BTFS
You can't colonise an existing planet. You must explore space and discover a new planet.