When investigating I found a lot of other stuff exit in /run - so no, I don’t think that is the issue.
In my tests - removing the live script’s reset of the machine-id resolves the issue fully.
This indicates that resetting the machine-id during boot is a bad idea when your goal is to auto-login a given user.
I dumped a copy of the manjaro-live script in
<iso-profiles-dir>/shared/manjaro/live-overlay/usr/bin/manjaro-live
The edited the file and commented the lines 46-48 - saved the file and build the profile.
As for the keymap settings - it seems that Gnome and Plasma Desktop may require the use of localectl set-keymap to pickup the keymap whereas xfce terminal pickup the keymap set by the kernel cmdline.
The desktop itself - tested using xfce - does not pickup the chosen locale from the kernel cmdline.