Yes, it’s the Podlove Publisher.
I did find a workaround that does the trick:
I use the blog post element in a simple WordPress page (not the alb) to get its shortcode. Then I change the post type manually to “podcast” (which is podlove’s post type) and place it in a code block element.
As far as I’m concerned that’s fine.

Although I’d generally like the blog post element to able to deal with custom post types.

Thanks for your assistance and your fast replies!
Kind regards,
Simon

Thanks for your reply!
I tried that in functions.php

function avf_alb_supported_post_types_mod( array $supported_post_types )
{
  $supported_post_types[] = 'podcast';
  return $supported_post_types;
}
add_filter('avf_alb_supported_post_types', 'avf_alb_supported_post_types_mod', 10, 1);

but I get the following error:

“Unable to communicate back with site to check for fatal errors, so the PHP change was reverted. You will need to upload your PHP file change by some other means, such as by using SFTP.”

What now?

Thanks very much for your help!