Instance feed
Is your feature request related to a problem? Please describe
On Wordpress with the Seriously Simply Podcasting plugin, there's the notion of a "main feed", an RSS feed containing all episodes from all the website's podcasts. In some cases, a podcast is started and published using this main feed while later growing into a podcast network as its ecosystem expands. The already published main feed therefore becomes more like a channel for all the individual podcasts, although listeners already subscribed will continue to use this main feed.
Admins migrating from Seriously Simple Podcasting to Castopod one would therefore need a way to represent the main feed in Castopod.
Describe the solution you'd like
I'd like for Castopod to replicate this feature in order to be able to smoothly and silently migrate a "main feed" structured podcast network to Castopod behind the scenes.
(This would also enable an "instance feed" of all podcasts being published on the same Castopod instance. This is useful since podcasts of instances are most often closely related on perspectives/themes etc.)
Describe alternatives you've considered
An alternative solution would be to use 3rd party tools to aggregate every individual Castopod podcast feed into a DIY main feed and continue to rely on that while also migrating to Castopod.