mmcli -m 0 --command=ATI

error: command failed: GDBus.Error:org.freedesktop.ModemManager1.Error.Core.Unauthorized: Cannot send AT command to modem: operation only allowed in debug mode

## set modem manager to debug mode

#stop modem in network manager

nmcli wwan off

sudo /etc/init.d/network-manager stop

#ps ax | grep -i "/usr/sbin/ModemManager"

#some time, need kill modem manager manunally.

#snap  start /snap/modem-manager/xxx/usr/sbin/ModemManager

sudo snap set modem-manager debug.enable=true

sudo snap restart modem-manager

sudo /etc/init.d/network-manager start

## Check

mmcli -m 0 --command=ATI

response: Quectel

EC20F

Revision: EC20CEFAGR08A01M4G