Lubuntu 18.04 LTS was released back on 27-April-2018, with three years of supported life by the Lubuntu team which is rapidly drawing to an end (five years applies to main Ubuntu Desktop, Server and packages found in the ‘main’ repository).
This means Lubuntu/LXDE components of your system will no longer receive security updates or fixes, plus we at Lubuntu won’t support it beyond this month, though your base Ubuntu components will continue to receive security updates from Ubuntu.
How can I check ?
To check the status for your own system, you can use ubuntu-support-status for example
guiverc@755-lubu:~$ ubuntu-support-status
Support status summary of '755-lubu':
You have 359 packages (18.9%) supported until April 2021 (Community - 3y)
You have 1324 packages (69.9%) supported until April 2023 (Canonical - 5y)
You have 2 packages (0.1%) supported until April 2021 (Canonical - 3y)
You have 3 packages (0.2%) that can not/no-longer be downloaded
You have 207 packages (10.9%) that are unsupported
Your Hardware Enablement Stack (HWE) is supported until April 2023.
Run with --show-unsupported, --show-supported or --show-all to see more details
guiverc@755-lubu:~$
Your installed systems will report differently to mine, as we all tend to add our own packages that suit our needs, and make our own systems unique. I suggest you run the command and explore your own systems results.
What should I do?
Modern Lubuntu with LXQt is ready to be installed.
If you like the stability of a long-term-support or LTS release, I’ll suggest Lubuntu 20.04 LTS. If you’re happy to release-upgrade every 6-9 months that very latest is our now stable Lubuntu 21.04 release, but I suspect if you’re still using Lubuntu 18.04 LTS, the LTS release is best for you.
Please note there is no supported upgrade path without re-install. As the Lubuntu 20.04 LTS release notes make clear
Note, due to the extensive changes required for the shift in desktop environments, the Lubuntu team does not support upgrading from 18.04 or below to any greater release. Doing so will result in a broken system. If you are on 18.04 or below and would like to upgrade, please do a fresh install.
How do I install Lubuntu 20.04 LTS
The best place to start is our Lubuntu manual, ie. https://manual.lubuntu.me/lts/
and I’ll suggest “Chapter 1 Installing Lubuntu”
FYI: If you go to manual.lubuntu.me, it by default shows the latest stable release. To view the manual pages for the latest LTS release (currently 20.04 LTS), change the “stable” to “lts” in the url.