Inconsistent $1 given to scripts between hostname and connectivity-change actions
According to https://developer.gnome.org/NetworkManager/stable/NetworkManager.html
Each script receives two arguments, the first being the interface name of the device an operation just happened on, and second the action. For device actions, the interface is the name of the kernel interface suitable for IP configuration. Thus it is either VPN_IP_IFACE, DEVICE_IP_IFACE, or DEVICE_IFACE, as applicable. For the hostname and connectivity-change actions it is always "none". <<
As found: $1 is NUL when $2 == connectivity-change $1 is none when $2 == hostname
Script used for the above screen capture of journalctl -u NetworkManager-dispatcher
test1.sh Above script placed in /etc/NetworkManager/dispatcher.d during ip link set enp1s0 down/up
System: Fedora 32 rpm -q NetworkManager
NetworkManager-1.22-10-1.fc32.x86_64