Charge for it. Rather than plead with people to support something they love, force them to.
— Valhalla Island
No matter how much people love your product or service, and no matter how good their intentions are about someday getting around to giving you that donation or buying your paid edition, they won’t get around to actually giving you money until you create some sort of pain point.
For software, that can be a time or feature limit. For example, you can try the program and make your great thing in it, but if you want to save it in a form that’s useful outside of the program itself, you have to pay. Or you can use the program for two months to get yourself completely hooked on it, then it’ll stop working unless you buy it. Or you can process ten tasks for free, but to process the eleventh and up, you need a license.
Content has fewer options, but it’s still a great model to use. Give away the first or most recent episode or chapter or article, then sell the rest.
Unfortunately, I’m not sure how well it works for podcasts. I would have expected it to work just as well as it does for other media, but look at what happened to The Ricky Gervais Show.