Add to sudoers
From https://linuxize.com/post/how-to-add-user-to-sudoers-in-ubuntu/
Log in as root with root password
su -
Add user to sudoers
usermod -aG sudo username
Add user to sudoers
echo "username ALL=(ALL:ALL) ALL" | sudo tee /etc/sudoers.d/username
Disconnect and reconnect to apply changes
exit
Now you can use sudo
sudo apt update