Safari doesn't recognize any of my installed RSS apps on macOS

Hi all, I have been having a problem for years that I'm just finally getting annoyed enough with to ask for help – I cannot get Safari to recognize any of my RSS reader applications when I click on an RSS subscription link – every time I click one, I get this message:

This is a link to an RSS feed. Would you like to search the App Store for apps that can display RSS feeds?

I've tried a number of readers at this point, but right now using Newsify.

For context, I've also tried installing SwiftDefaultApps to set Newsify as the default RSS app, but nothing has changed.

Really at a loss here; I do recall a long time ago being able to set an app as a default, but that doesn't seem to be the case in the UI anymore, so I wonder if something got stuck in preference files somewhere that I can't find.

Any help to get this reset/changed to Newsify would be huge! Thanks so much!

Adam