The thing about a cult is that it doesn’t need you in particular. It needs people. Ideally, idiots. So it doesn’t matter that a lot of people are leaving/will leave Twitter. The idiots will remain, and the platform will serve its purpose.
Traveller, or better yet 2300AD or Hostile for better fit on the setting with the same classic 2d6 rules. Cy_Borg or Stars Without Number for OSR.
Diaspora, Mindjammer, or Nova Praxis if you’re willing to try a more modern system (Fate), but the setting should be pretty close on them, depending on where in the story you want it to be. Diaspora should be a good fit if you want to explore different systems throughout a network of spheres.
BattleTech! That's the one. Didn't know they made an RPG out of it.
Firefly is an out of print Cortex Plus game by Margaret Weis Productions. It's in the list as well as Serenity (the Cortex Classic game by MWP, isn't IP licensing fun?).
Rifts is a classic, but also a very strange animal. And for some reason I thought Robotech was a minis game (must be confusing with something else).
Star Wars is already listed. I know those are technically different games, but I'm trying to keep the list as concise as possible (grouping the multiple versions of the same setting under one entry). I don't know much about the history of star wars RPG though. How would you summarize it? (WEG d6, d20, Fate)?
Yeah, definitely don’t get caught doing that.