Notable are Chapo Trap House, a communist/socialist podcast making nearly $2M a year, and Cum Town, a low production value comedy podcast pulling in almost $700k.
A similar scheme has worked in the screencast space as well, I recall Railscasts followed a similar approach of free "shows" and then you got more of the same if you paid. It seems to work really well as a format.
Chapo and C*town provide 2 RSS feeds. The free/paid feeds don’t show up next to each other in your podcast app because they’re named differently (dumb). No way to merge feeds in the popular podcast apps.
Smart producers like Stratechery/Dithering provide individual personal RSS feeds that combine the free and paid. And deliver only the free if your subscription lapses. But those are one-off CMSs that most Patreon podcasts don’t have the means to deploy.