PodCasts: top episodes: in this list of top episodes, how can I download any of the episodes presented? long-pressing of swiping do nothing useful.

You mean these charts, correct?

If you go to the top podcasts, you only see an overview of the most popular podcasts. You cannot download these from this overview. You have to select a single podcast for this.

It's different with the Top episodes tile: you can download podcast episodes there.