I’ve been using a Sony Epaper notebook for almost 2 years now and considering buying a Boox Note 5 or Air 2 (the remarkable didn’t make my short list)
They are running almost stock android and the quality seems better than remarkable.
I’ve watched My Deep Guide (https://youtube.com/c/MyDeepGuide) where they test every single feature of all note taking devices.
This article says that you have root access on the remarkable, but doing so will void the warranty.