To set up a feed redirect from Podiant to Pinecast, you'll need to delete your podcast on Podiant. Per their support article:
If you want to leave Podiant and use another provider, you'll need to delete your podcast from Podiant (this won't delete everything straight away). When you do so, you'll be asked if you want to provide a redirect URL. Your new podcast provider will give you your RSS feed URL (this is not the same as a website address, and it won't start with
http://feeds.podiant.co/ ). Paste that URL into the box when prompted, and we will instruct podcast apps to use your new feed.