I've in the past successfully set sharing of wireless Internet connection through Ethernet on Ubuntu 16.04 as described here. Unfortunately due to disk failure I install Ubuntu 18.04 LTS and cannot find anything similar to what is described in mentioned post. All menus are now different and I don't know where to look.
Follows these steps:
nm-connection-editorfrom the terminal
Click on the wired connection and select edit cog wheel below
Go to the ipv4 settings tab there in the Method select
Shared to Other Computers