There is an "Energy" setting, but that is for screen dim and lock. I think best to do updates in SSH. I have noticed many distros will fail in the GUI.
I also have the Manjaro Phosh on the eMMC card , and I the modem will shut down after booting, and unlocking the screen.
I also have the Manjaro Phosh on the eMMC card , and I the modem will shut down after booting, and unlocking the screen.