You'll find several opportunities other than mining which actually, in my opinion, isn't really passive, as any miner can tell you, it's almost a full time job really because you always have to monitor and maintain. First thing that comes to mind is investment in casino bankrolls, there are several which offer the chance.

Others like BitDice (in my signature) you can buy the native tokens that are linked to profit sharing every quarter. That's truly passive but of course carries a risk like all investments.