unmanaged Network Manager in ubuntu

After installing Ubuntu again, I noticed a problem, and the problem is that the Applet Device Manager displays an empty Wi-Fi tag. If I'm connecting to the Internet (by LAN), and when I click the right method, most options are inactive and below the Ethernet Network Device not managed! (Attached Pictures) I now imported my openvpn connection but I can not connect to it.

I also made these changes:

/etc/NetworkManager/NetworkManager.conf

First it was

[main]
plugins=ifupdown,keyfile
[ifupdown]
managed=false
[device]
wifi.scan-rand-mac-address=no

And I changed ifdown to this

[ifupdown]
managed = true

but problem not solve

Similarly, I can not connect to the VPN network, and I feel that these two problems are quite interrelated!

2 Answers

use this it worked out for me i am using ubuntu desktop 18.04

touch /etc/NetworkManager/conf.d/10-globally-managed-devices.conf
sudo service network-manager restart

As @JoshuaJohns states above, here is the answer for 20.04+:

1. As root, edit /etc/NetworkManager/NetworkManager.conf to match the following. You can use the command sudo nano /etc/NetworkManager/NetworkManager.conf to do so.

   [main]
   plugins=ifupdown,keyfile
   [ifupdown]
   managed=true
   [keyfile]
   unmanaged-devices=*,except:type:wifi,except:type:gsm,except:type:cdma,except:type:wwan,except:type:ethernet,except:type:vlan
   [device]
   wifi.scan-rand-mac-address=no

   Save and close the file. (In nano, you can do this by pressing CTRL-X, Y, then Enter.)

2. Restart the network manager service with sudo systemctl restart network-manager.