Mhm, interesting idea. I’ve adapted your code to my needs/wishes and now the feed looks and acts like it should, which is a major breakthrough! It isn’t a “valid” feed though, according to several Feed Validators. The main problem seems to be the pubdate/lastBuildDate, which aren’t in the correct format. The <lastBuildDate> currently looks like this:
<lastBuildDate>1469470566</lastBuildDate>
Instead of being in a format that complies with RFC-822 date-time. Same problem for the <pubDate>, which currently is empty. Is there anything I can do to get a “proper” date for each item and the feed itself? I’m currently reading up on this topic and comparing my template with the Podcast Plugin, but both seem to work with pages instead of files, so I’m stuck again. I’ll also have to yet test the feed on my live site, just to be shure this solution works fine with IFTTT/Feedly. Still, this helped a lot, thank you so much for this (possible) solution!
(By the way, the guid/id itself wasn’t as big of a problem, I simply changed
<guid><?php echo xml($item->id()) ?></guid>
to
<guid isPermaLink="false"><?php echo xml($item->hash()) ?></guid>
which seems to work fine.)