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.
Half as many cores, half the ram, and way less battery life due to higher power draw during suspend for some reason. It doesn't support the keyboard folio either. Depending on your criteria, one, or the other, is the better device.
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.