/etc/default/keyboard not taken into account at boot

Question

I'm trying to have a Mac keyboard behavior on my ubuntu/trusty32 virtual machine, and had some problems with it so far.

Using sudo dpkg-reconfigure keyboard-configuration seemed to work at first, but there was no way to keep the changes after a reboot, and the command sudo udevadm trigger --subsystem-match=input --action=change worked neither.

The /etc/default/keyboard content was:

XKBMODEL="macbook79"
XKBLAYOUT="fr"
XKBVARIANT=""
XKBOPTIONS="lv3:ralt_switch"

After some reading and tests I discovered that XKBVARIANT="mac" has better effects. I have now to type the command sudo udevadm trigger --subsystem-match=input --action=change to obtain the behavior expected, even after a reboot.

So I am wondering if I misread the sentence

After modifying /etc/default/keyboard, you can apply the changes to the Linux console by running setupcon. If X is configured to use that file too, then the changes will become visible to X only if udevadm trigger --subsystem-match=input --action=change is called, or the system is rebooted.

How to make the reboot take into account the new keyboard configuration?