My Traveller games have always been sandboxes, for the most part. I wanted to make a colonization campaign in a non-3I setting. My players wanted to be Sword Worlder ex-investigators investigating stuff and part-time merc work.
So that went off the rails quickly... fortunately before I had started generating star systems.
The only real railroading that occurred was the initial adventures: Flatlined/Death Station. Session Zero, they got retirement benefits and pooled their resources to build an upgrade. From there they had to get back to Sword World space, where they were supposed to be getting their ship, at which point they flashed back six months before being kidnapped. Then they had to find out how they got kidnapped (made for a HIGH degree of paranoia and the players felt any moment the hammer could drop, but were trying to play as if their characters didn't.
Once that arc resolved, they've been wandering around picking from sets of odd jobs that they'd expressed interest in during the previous game.