Quoted from Distrowatch.com: The Lubuntu team has been planning a migration from using the LXDE desktop to running LXQt as the default desktop for a while now. With Lubuntu 18.10 now on the horizon, the developers have made the switch official. "This is the first Lubuntu milestone to be released with LXQt as the main desktop environment. The Lubuntu project, in 18.10 and successive releases, will no longer support the LXDE desktop environment or tools, and will instead focus on the LXQt desktop environment." Additional information on Lubuntu's 18.10 Beta release can be found in the project's announcement.
Here's Lubuntu Lenny Cuttlefish mascot, BTW: https://lubuntu.me/wp-content/uploads/2018/09/lennyfish.png (tried to insert the image but it didn't work. Must be disabled in the forum software...)