I've used freshrss for a while. Web based, self hostable.
Linux
Everything about Linux
RULES
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Be nice to each other.
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No memes or pictures of Linux in the wild.
If you're open to web-based readers, I personally use The Old Reader, which is modeled on Google Reader: https://theoldreader.com/
I also looked into NewsBlur sometime back, especially because there's a package for integrating it into Emacs, but I didn't pursue it any further: https://newsblur.com/
I use Vivaldi with it build-in feed reader at work, also Nextcloud News for almost everything else.
https://github.com/martinrotter/rssguard
An important function of RSS Guard for me is the extensive filter function (https://github.com/martinrotter/rssguard/blob/master/resources/docs/Documentation.md#fltr).
I use Thunderbird for now. Also going with Fluentreader sometimes.