Users installing from ISO often have trouble with Netplan on Ubuntu, an example below is given as a reference:
network: version: 2 renderer: networkd ethernets: ens3: critical: true dhcp4: false dhcp6: false addresses: - 123.45.6.78/23 - 2a0f:93c1:99:123::4567/64 routes : - to: 0.0.0.0/0 via: 123.45.6.1 - to: "2a0f:93c1:99::1/128" scope: link - to: "::/0" via: "2a0f:93c1:99::0001" on-link: true nameservers: addresses: - 8.8.8.8 - 8.8.4.4 - 2001:4860:4860::8888 - 2001:4860:4860::8844