Hello,
You are right, I tested, at the menu of the bootloader, press 6 to go to the bootloader prompt and write set OFFICE_NETWORK=YES <Enter>, then boot <Enter> and with the kenv -q variable_name you get the answer.
Great
Thank you for your help and for your brain
(I know that moving from lx to FBSD, it will be a small step for humanity but a very big one for me)