Change keyboard layout on your own created Linux live system for example Xubuntu

Edit this file /etc/default/keyboard

Open as sudo or root this file with vim

# vim /etc/default/keyboard

Then for example the 'en' to this

XKBLAYOUT= 'en'

to

XKBLAYOUT= 'de'

:wq

Done

Further reading:

https://linoxide.com/configure-keyboard-ubuntu/