I ran into this exact problem earlier, I thought it was an issue with running the game through Proton, every fleet I faced was just one tutorial fighter, “Tactile Hallucination”, there was no battle history displayed for said one fighter fleet.
While the concept of one immortal fighter pilot opposing my fleet in every star system I ever try to invade is funny, it wasn’t much of a challenge.
The only interim solution I can think of is manually creating fleets and trying to force them into the campaign as enemies, though I don’t know how you’d do that.