sudo apt update
sudo apt upgrade

ip a
ip a show eth0

dig +short myip.opendns.com @resolver1.opendns.com
dig TXT +short o-o.myaddr.l.google.com @ns1.google.com | awk -F'"' '{ print $2}'
wget https://git.io/vpn -O openvpn-install.sh
chmod +x openvpn-install.sh

sudo ./openvpn-install.sh

Sample session from AWS/Lightsail where my cloud server is behind NAT:

Sample session from Linode/DO server where cloud server has Direct Public

To avoid problem always choose DNS as 1.1.1.1 or Google DNS. Those are fast DNS server and reached from anywhere on the Internet.