Share network connection peer-to-peer

Computer A - having internet connection- using phone tether or wlan

nmcli connection modify myconnection ipv4.method shared
sudo systemctl restart NetworkManager

Computer B having no network

nmcli connection modify myconnection ipv4.method auto
sudo systemctl restart NetworkManager

Connect ethernet cable

Source Connect 2 PCs, one has internet via USB-tethering - Manjaro Linux Forum