The ReMarkable 2 needs the proprietary Xochitl binary to update the screen (there's a shim, but it needs to be updated every time Xochitl updates), but the ReMarkable 1 doesn't have this problem, and already has a port of Parabola Linux, Parabola-RM (no WiFi due to Linux-libre, although you can compile it with them included): http://www.davisr.me/projects/parabola-rm/

Plus, the ReMarkable 1 has a total of four hardware buttons, and is even 50g lighter! Plus it's power button doesn't get stuck.