It’s very easy! All you have to know ist
dpkg-reconfigure
can be called with several options where the most important are “keyboard-configuration” and “tzdata”. If you are living in a country where english-keyboard-layouts are used then you don’t know the trouble it causes, if you have to use a physical keyboard with your caps-layout and an english-software-layout.
So all that non-english-keyboard-users have to know ist: run
dpkg-reconfigure keyboard-configuration
and after that
dpkg-reconfigure tzdata
It would be nice to see this simple information in the wiki “How to setup a nextcloud-pi” for Odroid-users.