On the librem 13 v2 and v3, the scancode 56 should be mapped to keycode 43 (backslash), I have a fix in place locally that I pulled from the purism forums: https://forums.puri.sm/t/keyboard-layout-unable-to-recognize-pipe/2022/10
Basically I override the current keyboard udev rules with my own in /etc/udev/hwdb.d/90-keyboard.hwdb
Here's my Librem 13v3's /sys/class/dmi/id/modalias
side note: it's weird that the v3 is actually called the v2 version 2. It threw me off when I first got this machine.