I've just found a solution for this problem, so I wanna share it in case someone bumps into it

And Emerson -> 'you should broadcast your SSID' isn't very helpful in case you're a user, not an admin of a wifi network, right?
So, the solution is quite simple, in your wpa_supplicant.conf:
network={
ssid="the non broadcasted ssid"
scan_ssid=1
...
}
Hope that helps.