I don't know about "best", but I've tried many, Reeder, Feedly etc, for many years. These are not OSS though, but Reeder was my favorite of the bunch.

I settled on running NewsBlur on an OVH instance, it's open source and so are the apps. https://github.com/samuelclay/newsblur

On the desktop I use the default web interface, it runs and looks nice. A bit too many batteries included, but you can turn things off.

It's Django, so you can vibe code to your heart's delight. I did.