Mugen no Ryvius, 11-nin Iru! Recommendations
A bunch teenagers being thrown onto a mysterious space ship, and they found out their way surviving. Trust, betrayal, friendship, angst shown under various situations.
They were 11 deals only with internal conflicts, being a 90 min movie a lot development has to be cut short. Also rewatchability is a bit low when you get spoiled at the end resolution.
Infinite Ryvius being a 26 episode TV series, has a lot of time to develop its plot, and characters, despite the casts are huge. Teens in this series have to deal with outsider attacking and internal conflicts, so the story seems fuller than They were 11.
Bunch of kids/young adults trapped on a ship with mechanical issues and other problems? Check. Suspicions on other characters that leads to all different kind of turmoil and nearly breaks apart the group and the societal structure of the community on the ship? Check. If you couldn't tell which series I was talking about with these two statements, it's because the shows are very similar and both great.