It likely depends on the particularities of his contract, but my guess is that he couldn't be stopped from releasing a new podcast even if his contract explicit

It likely depends on the particularities of his contract, but my guess is that he couldn't be stopped from releasing a new podcast even if his contract explicity said he can't. Spotify would be hard-pressed to justify a non-compete when they fire him and pull his episodes down. And his contract might very well include provisions covering exactly this sort of situation. No agent/lawyer worth their salt would let a public figure sign an exclusive deal that lets the company black list their client. I doubt Spotify can pull him off their platform without breaching their end of the contract.