After reading a few Posts about going rock no atmosphere as a start trait so you can use rock moons I tried it and still had a dome on the moon. It was rock (As was I). This intended?
You could still get a dome symbol if you have the right atmosphere for your race: If you colonise a planet without putting any population on it (ie forgetting to load your colony ship with pop) it will be domed until you get some native breathers on there.
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"Pinky, are you pondering what I'm pondering?"
"Uh, I think so, Brain, but balancing a family and a career ... oooh, it's all too much for me. "
Rock/none races have a big drawback. There are no gas giants with that atmosphere.
This makes these races spread over many, rather smallish planets. Which is not the best for defense purposes.
I noticed this drawback for "none"-breathers and thought it would be good if this was balanced out - it would need a hardcoded change, but what if non-breathers has reduced Life Support requirments on their ships?