I teleported to an enemy ship, killed all the crew I found, and then returned to my own ship, but the game didn't reward me with anything. I thought perhaps my scrap would increase after I jumped away, but it didn't. What must I do to recover resources from a captured ship once the crew is dead?
There's a chance that the ship you boarded had a Cloning Bay, in which case it needs to be destroyed for the crew to be considered fully dead. If that's not the case, you said you killed "all the crew you found", which makes me think you do not have improved sensors to see the inside of enemy ships. In that case, it's possible that you simply missed some crewmembers.