i did some more testing with xterm, lxterminal, qterminal, and urxvt in the latest manjaro lxqt.
the commands you mentioned worked in all of them, except urxvt:
[manjaro@manjaro ~]$ sudo mhwd-chroot
/usr/bin/mhwd-chroot: Zeile 18: rxvt: Kommando nicht gefunden.
[manjaro@manjaro ~]$ gksu mhwd-chroot
(gksu:3311): Gtk-WARNING **: Unable to locate theme engine in module_path: "adwaita",
(gksu:3311): Gtk-WARNING **: Unable to locate theme engine in module_path: "adwaita",
/usr/bin/mhwd-chroot: Zeile 18: rxvt: Kommando nicht gefunden.
but "sudo mhwd-chroot-shell works.
i remember it worked in my last test in urxvt. this is strange.
p.s.: i translate this line:
Zeile 18: rxvt: Kommando nicht gefunden.
line 18: rxvt: command not found.