Input lag, non-paper feel and heavy cloud-pushing are not the case with Remarkable. Documents can be uploaded and downloaded locally via a browser. Here is a good starting point with what can be done with a modded device, including self-hosting a replacement for Remarkable's cloud services and installing a package manager to make installing further community software pretty easy. And for someone comfortable with the terminal, the Entware system lets you choose from a whole bunch of standard open-source packages you can add.

This isn't going to give you what you'd think of as "a Linux desktop" or even Android-like experience, but OP wasn't asking for that.