Fixed: Ubuntu networkmanager device strickly unmanaged

By default, NetworkManager does not manage interfaces that appear in /etc/network/interfaces. You can change this behaviour.

sudo vim /etc/NetworkManager/NetworkManager.conf

Change the line managed=false to managed=true

$ sudo systemctl restart NetworkManager

Another way: Remove the interface from /etc/network/interfaces.

Only keep the following inside /etc/network/interfaces:

auto lo

iface lo inet loopback

$ sudo systemctl restart NetworkManager