I have been asked by @mvader (Victron Energy) to repost this issue here.
I have an oddity on my Pi 4 B+ v1.5 running Victron Venus OS v2.90~26 large in that a keyboard connected directly via USB and displaying on the HDMI is mapped for a US keyboard whilst connecting by SSH from a different machine gives me the UK keyboard layout I desire.
I am happy to use SSH but I would also like to know if it is simple to change the mapping in busybox for specific inputs (and how to do it) or is this is a more general issue which needs further work?