Stop everyone, problem solved!!!
I did a fresh install of the armbian image to start fresh.
Then I ran "sudo apt-get update", then ran "sudo apt-get install armbian-firmware-full". At the end of this update I noticed that with "lsusb" the Realtek device had a strange "CD rom mode". Reading on the net I installed "sudo apt-get install usb-modeswitch" then executed at least twice the command "sudo usb_modeswitch -KW -v 0bda -p 1a2b". Then I found the wlan interface. With "sudo armbian-config" I configured the WiFi and now everything works fine! 💪
The only thing I don't like so much is that the WiFi interface is not called wlan0 but wlxa0d768106782 which is not very simple!
Thanks Werner for the tip, I hope it can be useful to someone else 😀
