This post got me to try out selfoss but after it being pretty buggy and unable to fetch 50% of the feeds I was interested in, I looked elsewhere. I wanted to install Tiny Tiny RSS but the instructions weren't my thing. Finally, I settled on FreshRSS and I love it. All the feeds work. The only complaint I have is that, at least it seems, you need to manually add labels to each article and instead just put a feed under a category. I wish I could put feeds under any amount of labels or categories I want. Maybe there's an extension for it that I have not seen yet.
What I meant was assigning multiple tags (like "tech", "security", "foss", etc) automatically to posts in a feed instead of needing to manually assign them to each article. So if I then want to filter all posts with "security" and "foss" I could choose those two tags to get the filtered results. Can it do that?