TecMint published a tutorial about installing Lubuntu 20.04 based on the LXQT desktop.

Install Lubuntu 20.04 - A Lightweight Linux Desktop Environment

Lubuntu is an open-source distribution of Linux based on Ubuntu. It is lightweight, fewer resource hungry, more energy-efficient and uses an LXQT desktop environment. The initial release of Lubuntu has LXDE as their desktop environment but with version 18.04 it uses LXQT. If you are an existing user of Lubuntu who uses LXDE then migrating to higher versions that use LXQT will be challenging.

Install Lubuntu 20.04 - A Lightweight Linux Desktop Environment