NETWORK CONFIG ON UBUNTU

 This has been changed since the last time I worked on ubuntu and now it totally differs from my debian knowledge. There is nothing complicated about it. The config file is just placed elsewhere and formulated differently. Then the network restart command and the networking system is also different. 

Back in the day it was the "if up if down" or "ifupdown" and now it is the Netplan service.

Check with this command which one are you running:

   dpkg -l | grep -E '(netplan|ifupdown)'

Check your card name with:

   ip a

Then edit your network file:

Instead of /etc/network/interfaces it is in a .yaml Netplan file

            # /etc/netplan/00-netcfg.yaml (config file location)
           
            network:         # start of network config block               
              version: 2     # use of Netplan version 2
              renderer: networkd     # system service provided by systemd
              ethernets:    # section of ethernet interface config
                enp0s3:     # interface logical name            
                   addresses:
                    - 192.168.1.40/24         # IP address and subnet mask
                   routes:                   
                    - to: default            # gateway, default
                     via: 192.168.1.254      # router ip
                   nameservers:
                    addresses: [8.8.8.8, 1.1.1.1]         # DNS server IPs

Then instead of systemctl restart networking.service
                systemctl restart network-manager

We simply use:
     netplan apply   

This is how simple it is still to configure a network card in linux / Ubuntu. You can find all info, very clearly explained here:

• https://ubuntu.com/server/docs/configuring-networks

 _dnhyper