Have always been curious about AntennaPod. Was about to switch from PocketCasts earlier this year but turns out PocketCasts became open source a little over a year ago, October 2022.
Still curious about AntennaPod but PocketCasts has been and continues to work super well and has a web/desktop (PWA) client so may just stick with it. Mobile app repos below btw.
I think it's usable for free though I'm not sure to what degree since I picked up a one time payment lifetime plus subscription some years ago. I see it's sadly now only free or monthly subscription. 😔