Hey there,
The Rubicon system has spawned in my current Stellaris run, and with a little Googling traced it back to this mod (I have a large number installed, so it can be hard to tell which mod is responsible for anything).

As with most alien powers, their ships start unidentified and with the 'Investigate' prompt - however, there is not a matching special project for their ships, even after visiting one of their patrolled neighbouring systems and receiving an event related to them.

Unfortunately I've encountered a similar issue with an AI-controlled empire, due to them having an empty empire name. So I'm not sure if this is intended behaviour or not.

So, tl;dr:
The aliens in the Rubicon system: Are you supposed to be able to talk to them / decipher their language? Is this linked to a specific event (which may not have yet triggered for me) or system? Or are they supposed to forever remain mysterious?