Ubuntu announced its 18.04 (Bionic Beaver) release five years ago. The standard support period will end on 31/May/2023 unless you get Extended Security Maintenance (ESM) support contract. Most users upgrading to 20.04 LTS will get upgrades after the standard EOL date. https://www.cyberciti.biz/faq/upgrade-ubuntu-18-04-to-20-04-lts-using-command-line/