Thanks Jukk. In fact I did, sorry if I did not tear it down from the beginning, but I still get the same error without much more details than what you already understood from the full output above:

Mounting is not the issue, chrooting in Arch is no issue either, but issues appear when start_xwayland_user_shell.sh is started:

But I suppose it's nothing, probably just due to the fact that it never worked before in this rootfs (remember that I deleted the one I unpacked as nemo and unpacked a new one as root) so there is no .lock file to delete in Arch's system.

Kinda works I guess since there's an output (not sure this is the expected output though?), but regardless of the next command to be executed (could be something as simple as ls or pwd), a segmentation fault will appear. In fact, the segmentation fault comes with this kwin_wayland command, but only appears in the next command due to the & at the end. Without the &, I just get the segmentation fault without the 11469 output.

From there, and until this issue is solved, I'm not sure it makes much sense to further investigate the next commands in the script (export DISPLAY=:0, then xhost +, then sudo -u nemo bash /usr/share/easychroot/scripts/start_de.sh "$Start_DE") as they are probably influenced by this error.

Is kwin_wayland causing a segmentation fault for you too guys? Maybe someone using a Jolla C as well, or at least an ARM device?