Curiously the command mmcli -m 0 returns the following as part of its output:
Status | lock: 'unknown'
| unlock retries: 'unknown'
| state: 'failed'
| failed reason: 'sim-missing'
| power state: 'unknown'
| access tech: 'unknown'
| signal quality: '0' (cached)
It is definitely not the case that the SIM is missing, I can even confirm that under Windows 10 the system is working and the device can reach the Internet.
After the configuration suggested above (command nmcli c add type gsm ifname <interface> con-name <name> apn <operator_apn>), I cannot see any error; still, I can't access the web.
Any guess on how I could troubleshoot this problem? Thanks in advance.
pi@raspberrypi:~ $ uname -a
Linux raspberrypi 4.19.66-v7+ #1253 SMP Thu Aug 15 11:49:46 BST 2019 armv7l GNU/Linux
pi@raspberrypi:~ $ lsb_release -a
No LSB modules are available.
Distributor ID: Raspbian
Description: Raspbian GNU/Linux 9.13 (stretch)
[UPDATE]: When I try to take up my new connection, the system returns:
Error: Connection activation failed: No suitable device found for this connection.