Add support for an alternate RSS link (for podcasts)

I implemented something like this today as a custom code plugin for Metatag 2.0.x, which can support multiple RSS links, but without the (apparently optional, but possibly desirable) title attributes. I'm not entirely sure how to include fields for both attributes, much less have multiple values for both, if that's even practical or possible with the module's UI. I could roll what I have into a patch for 2.0.x, if there's interest, but would need to know what group and weight value I should assign it.

No podcast here, but I wanted to properly associate an RSS feed for the site without the icon at the bottom of the front page view. I also wanted to add the tag to article pages, for Google Discover purposes.

We've just run into the same demand to add an RSS feed on certain content types (that are contained in the RSS) for Google Discover:
https://developers.google.com/search/docs/appearance/google-discover?hl=de

What we'd need is being able to add
<link rel="alternate" type="application/rss+xml" href="https://example.com/rss.xml">

Drupal / Views does this on the view itself, where the newsfeed is defined, but has no options to also attach it to other pages. Also other Metatag contrib modules don't seem to allow that?

I'd be happy to include this tag if someone wants to put together a patch / merge request for it.

We're almost there... With ver 2.1 custom_tag module, we can achieve rel=alternate and href=link. It just misses the type tag.