changing bios key for VM on Ubuntu / Linux Mint / Debian hosts,
Go to host pc Open any terminal and remember, you don't have to be root
BoxManage setextradata "VM-NAME" VBoxInternal/Devices/pcbios/0/Config/DmiSystemSerial "SERIAL-YOU-WANT"
FOR EXAMPLE
VBoxManage setextradata "win10" VBoxInternal/Devices/pcbios/0/Config/DmiSystemSerial "aabbccdd12"