For technology, I'm going to roll for the races, not the planets...
Fey - Technology: 9 (classical antiquity); Spelljamming Technology Knowledge: 4 (none)
Aberrations - Technology: 3 (none); Spelljamming Technology Knowledge: 15 (moderate)
Undead - Technology: 4 (primitive); Spelljamming Technology Knowledge: 16 (moderate)
Well, that changes things.
It looks like the fey have managed to find a way to live in this system without the knowledge of spelljamming. Perhaps they live on one of the worlds in a dome with an atmosphere. Meanwhile, the aberrations don't have any technology but are aware of how spelljamming tech works. Perhaps a group of mind flayers became stranded in the system and must live savagely. Perhaps they survive by feasting on the fey while avoiding the undead.
Now, the undead have primitive technology, which means about what you think it does. Stone tools and weapons, almost no metallurgy, and hunter-gathers/herders. Perhaps the undead herd aberrations for their food. Of course, the undead don't need food and water but their slave-food will need it. I foresee intelligent, ghoul-like creatures ranging across barren worlds hunting aberrations that may or may not need to breathe. Now, these undead beings are also aware of spelljamming tech. Hmm....