Lack of a decent RSS client is one of the major things keeping me on an iPad over an e-ink tablet. I wish manufacturers like Remarkable would get serious about having software platforms.
(n.b. haven't tried it, but I'm a happy user of KOReader for a couple of years now.)
I built a web-based RSS reader for the Kindle browser (but it should work on other e-ink devices too).
You can read feeds online or download them directly on your device.
Please try it and let me know what you think!