I don't see anything in the interface for doing a clean shutdown or reboot. Is the only way to yank the power cable? This feels a bit brutal, considering it's a Linux machine under the hood. I'm especially worried about doing this whilst apparently stalled in the middle of upgrading all plugins.
The system is designed for yanking the power cable.
In any case ssh firstname.lastname@example.org (password: mod) then reboot should do the trick for manual reboot.
PS. ssh is only available via USB cable network -- not bluetooth (at least not by default)
Note that this is not officially supported at all.
The controller display does not recognize a manual reboot, and might have issues if you have menus or addressings open.
So does this mean the only (and best) way to reboot is pull the power plug and then plug back in?