Sometimes, Ubuntu20 would "waste time" at this prompt: "A stop job is running for unattended upgrades shutdown (10s / 30min)"....thus it will wait for the next 30mins before continuing with the installation.
Allow the server to boot, and as root disable unattended upgrades
command: sudo dpkg-reconfigure unattended-upgrades
then select "NO" at the next prompt,
remove unattended upgrades with this command: apt remove unattended-upgrades
then update: apt update
