Ubuntu non LTS to LTS in the future

Solution 1:

Upgrade to a new Ubuntu release is always provided "over the air" if your current installation is still supported, i.e. not reached its respective end of life which is usually 9 months for a non-LTS versions and 5 years for LTS versions. These updates are provided irrespective of the fact that your installation is LTS or non-LTS. It is also to be noted that the release upgrades that would be provided can be managed via /etc/update-manager/release-upgrades or Software and Updates app in Upgrades tab.

Since 18.10 is non-LTS, you need to make multiple jumps (18.10→19.04→19.10→20.04) to get 20.04 LTS version. Whenever new release is available, to update simply run:

sudo do-release-upgrade

If you want to avoid such many jumps, install latest LTS, i.e. 18.04. In case of LTS, generally upgrades to LTS are not available until first point release, i.e. YY.MM.1, which is usually released in the month of July. This is because it may happen that there are some bugs reported in the initial version. So, you might not get updates for 20.04 but directly for 20.04.1 may be in July 2020.