Occasionally I get magnet links to torrent files in the title of posts. I could click on them and that opened my torrent client app. This no longer works. I can ‘Copy link’ the title and paste that in my torrent client app and that works so the magnet links are valid.
I do not know if this change of behaviour was caused by changes in NNW or macOS.
I’m not sure when it changed. It was working until a few weeks ago. Magnet links in web pages still work fine in Safari (which is the browser set to open links to in NNW).