Lubuntu 19.04 (Disco Dingo) will reach End of Life on Thursday, January 23, 2020. This means that after that date there will be no further security updates or bugfixes released. We highly recommend that you update to 19.10 as soon as possible if you are still running 19.04.
After January 23rd, the only supported releases of Lubuntu will be 18.04, with LXDE, and 19.10, with LXQt. All other releases of Lubuntu will be considered unsupported, and will no longer receive any further updates from the Lubuntu team.
You can find instructions on how to upgrade your Lubuntu installation here at our manual page.
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. The installation image can be obtained from our downloads page.