I found the crucial moment, putting 'ping's before and after every single step.
The mysterious problem is happening when "Disabling systemd-resolved DNSStubListener and restarting systemd-resolved"
See this link to my fork: This is the moment... before I can resolve name, just at the end of this phase, I cannot no more resolve name.
This is the debug output, sorry for strange format, is captured
"[i] Ping 2", "", "PING google.it (216.58.205.99) 56(84) bytes of data.", "64 bytes from mil04s26-in-f3.1e100.net (216.58.205.99): icmp_seq=1 ttl=54 time=12.1 ms ",
"--- google.it ping statistics ---", "1 packets transmitted, 1 received, 0% packet loss, time 0ms",
"rtt min/avg/max/mdev = 12.175/12.175/12.175/0.000 ms",
"[i] Testing if systemd-resolved is enabled ",
"[i] Testing if systemd-resolved DNSStub-Listener is active",
"[✓] Disabling systemd-resolved DNSStubListener and restarting systemd-resolved",
"[i] Ping 3", "", "ping: google.it: Errore temporaneo nella risoluzione del nome"