According to this guy you have to go into the show caring about these characters and you'll like it if you're a Rebels fan. It feels like Rebels season 5.
Lol, that's me out then.
Apparently the show assumes you know and care about these characters and havd watched the cartoon shows, though doesn't think anyone will be confused if they haven't.
Honestly even if you haven't watched Rebels, these are still some pretty fun and colorful characters that should be far more compelling than most of the other supporting characters we've gotten in the Disney+ shows.
And if you don't know their full history, it will be no different from watching the OT back when we hardly knew anybody's backstory.