Issue with Avahi network service discovery on xUbuntu 16.04 LTS

On xUbuntu 16.04 LTS, I was constantly having the following error message on startup:

Network service discovery disabled. Your current network has a .local domain, which is not 
recommended and incompatible with the Avahi network service discovery. The service has been disabled.

As my friend Stéphanie is very sensitive to error messages on her computer (and I am her sysadmin), I started searching where this issue came from, when she asked for help. It turned out to be linked to the start of avahi daemon, which is only useful for a very limited number of applications, mainly using the local network and almost all being developed by Apple. So the solution was pretty simple: I prevented avahi daemon to start by editing the file (admin mode) /etc/default/avahi-daemon and by changing the option