Hardcore History is great.
It's not as professional, but I really like a podcast called Liar City. Doesn't come out that much, but lots of old episodes to catch up on.
In the true crime genre where they cover one case over a season like serial, I like Someone Knows Something, especially seasons 2 and 3. Really good, and it's professional. There's also a true crime podcast called Dirty John that covers a case and is super interesting. Many more in that genre are really good. I haven't found that many in the "one crime per episode" style that I really get into.
I listen to a lot of comedy podcasts, but of a certain taste, so I'm always hesitant to recommend comedy. How Did This Get Made, about bad movies, is pretty great and accessible.