The Rebels can survive on ice planets, they can build colonies of up to 9 million colonists. On desert planets, 60 clans survive. Dark Sense does not find rebels.
Rebel ships can ground attack enemy planets, to destroy their infrastructure.
Rebel ships are rather standard. They are immune to attacking planets. Rebel carriers have service robots on board which automatically build fighters from cargo as soon as the required amount of minerals is available. Rebels can build a rather large hyperdrive ship.
