I got it fixed. First I deleted the game via steam and reinstalled it, but this didn't help. Now i got it working by deleting the game via steam AND deleted some remaining data within the ONI folder in steam (no mod data). After that i made a new clean installement and it works just fine. I hope this works for you too Moonshade. It seems that a deletion via steam does not remove all the ONI game files, atleast in my case.
Got the same problem. I'm picking an asteroid, choosing my dupes and hit the embark button and then the game crashes when loading into the map. Tested it like 10 times with different setups (asteroid dupe combinations and ofc no mods activated).