I can see the appeal of having a full feed RSS so you don't subscribe in two places, But I don't login and only use the RSS feeds. I use TT-RSS and just do subfolders for my feeds. If I click the Youtube folder it displays all the youtube feeds in order but I still have the option to drill down per channel.

> I also like having a single feed with new vids from every channel I’m subscribed to on invidious which I don’t think is possible on YouTube

That seems contrary to the idea that your RSS reader should be the one place you control your subscriptions from.

Which is something of a general problem—an on-site list of subscriptions is certainly also useful in ways the reader can’t really replicate in a generic way, yet it’s in the user’s interest to be the only one in control of that list instead of involving the website in it.

I can’t think of a good way to deal with this.

The only place I have ever seen a "next" link for an RSS feed is WordPress. Sort of a pagination thing you can do with the URL.

RSS isn't supposed to be an Archive, It's an activity feed. Best practice has providers trimming the XML file to the latest X items.

You can stylize and embed things like a next link in an RSS feed but that should just point you to yet another XML file and it's not part of the standard.