I've been searching for a cross-platform desktop RSS reader. Thunderbird is what I use for now and I would stop looking if I could just filter URLs but the filtering only seems to be built for email, which works if the URL is in the "body" of the feed item, but not all feeds are structured like that (e.g. HN). RSSOwl looks real promising but doesn't run for me on Windows 10 and hasn't been updated in 2 years. I'd prefer a standalone RSS reader, not a email client with RSS tacked on. I looked at everything in the comments so far but they all fall a little short.