According to Disney canon, the Rancor in Return of the Jedi is a male named Pateesa. Though at this point, I wouldn’t be surprised if they just changed their own canon again like they did in the season premiere with Kanan. If they don’t, it’s probably the rancor Jabba has prior to the one we see in the film.
As for the show as a whole, I just am not as impressed with it as every other Filoni shows. It feels like a Mando remake to me: the Bad Batch (Mando) takes a child under their wing and they go around the galaxy running into dangerous encounters or taking jobs for money. There’s no overarching plot really, each episode is its own adventure, which alone isn’t a bad thing. But week after week now after Mando followed the same formula, it’s getting kind of old to me. I guess I was just hoping for more, but we’ll see if they change it up before the end of the season.