Characters like Han Solo or the Rouge Traders of 40k are well loved, and I've been thinking recently about whether someone like them could exist in a no-FTL universe.

Within a heavily settled solar system someone could clearly get around by pretending to be legitimate transports, or doing legitimate odd jobs, ala Firefly or The Expanse.

Between star systems that trade routinely, hitchhiking on a ship accelerated by pushing lasers, Orion drives, or other more futuristic tech is possible, as is pretending to be a legitimate operator and making use of the interstellar highways yourself.

But is it possible to move between star systems that don't expect your arrival? None of the ways to sail the stars quickly are subtle. Orion drives, pushing lasers, antimatter, black hole feeding,etc are all very visible.

A drive that warps space like an Alcubierre Drive seems less obvious but probably would create characteristic gravitational lensing effects. I have no idea how easily visible they would be

Two options stand out that are limited to posthumans or aliens. A very stable, long-lived organism can slowly travel the stars like a Von Neumann Probe, going where it pleases under the guise of an interstellar comet, at least until some hapless mining crew dig it up. A very light organism, like some living neutrino construct or tiny AI on a breakthrough starshot chip may not need massive visible pushing infrastructure to slow down and speed up...

But for humans or things that think on normal human time and size scales, is the idea of going around on one's own ship like the millennium falcon to different star systems impossible except through social engineering?