Indeed, Patreon has private feeds for patrons for exclusive content. That's a decent solution but it's platform-specific, which is both a bad thing (not easily used elsewhere) and good (backwards compatible with good old RSS).
Did not know Patreon's tech was lock-in. I subscribe to a podcast on Spotify and they give you a private URL that you can feed to any app. If you are worried about malicious customers sharing the URL you may likely enable some form of rate limiting (e.g. the server may only serve up to x MiB/month on this URL)
