I was hoping for this to work but it doesn't parse the full content. Weirdly also it didn't import correctly the opml file, the folders where there but they didn't have the rss link.
Nextcloud's news reader is pretty good -- but you need to host a Nextcloud instance first :) (Hint: you should, to free yourself from google/icloud or whatever you use)
I'm a fan of KDEs Akregator. It does a great job as a feed reader and shows the contwnt of an entry in a simplified reader mode. However some feeds jist dont display the full arricle in their feed entries so you'd have to follow a link there. But even thats sth that makes Akregator awesome: you can specify the command thats used to follow a link and most browsers have the option to open a page in reader mode via the commandline. So from what I gathered thia should pretty much do all you want it to and then some.
I tend to use either Newsboat or Elfeed. The first one is command line, the second is Emacs. So they're both text-based. Might not be precisely what you're looking for, but with the right choice of terminal font and easy-on-the-eyes colours, I find it a pleasant reading experience without distraction.
Feedbin. Not a Linux app, but a web app. And not FOSS or self hosted. Just a really great app run by great people for a great price. Parses full content and has a pretty nice API.