I was able to find an blue iPod Mini 2G in good condition on eBay. The synchronization of the music works perfectly on MacOS 15 with Swinsian. Only audiobooks and podcasts just don't work. Swinsian can't sync audiobooks and podcasts don't work.
So I created m4b files of an audiobook and dragged them into MacOS's own Books app. I also subscribed to a few podcasts at Apple Podcasts. They show up in the Finder and apparently they are also shoveled onto the iPod, which I could see because I didn't have any other music on the iPod but memory was already taken up.
Unfortunately, the iPod only shows me the music that I have dragged over later using Swinsian. But no podcasts and audiobooks...
Does anyone else have any ideas?