So I built my own over a weekend, mostly so I'd stop losing the essays I meant to come back to. Clean reader, audio for walks, search, public collections. It's free. It's rough in places and things will break, but I'll keep fixing them.
The browser extension is open source: https://github.com/mahmoudalwadia/readit-extension
The app is the small part though. I wrote about why I read essays here: https://mahmoudalwadia.com/writing/essays