LXQt is a lightweight Qt desktop environment.

It will not get in your way. It will not hang or slow down your system. It is focused on being a classic desktop with a modern look and feel.

• Modular components
• Powerful file manager
• Customize appearance everywhere
• Panel(s) with many plugins and settings
• X11 Window Manager agnostic
• Seven Wayland compositors supported

Applications

• PcManFm-qt - File Manager
• Lximage-qt - Image Viewer
• QTerminal - Terminal Emulator
• Qps - Process Viewer
• Screengrab - Screen Capturer
• LXQt-archiver - Archive Manager
• LXQt-runner - Application launcher and calculator

LXQt is available for all major Linux and BSD distributions so you may just try it out on your system or in a VM.
More information about installing can be found in the LXQt Wiki.

Historically, LXQt was the product of the merge between LXDE-Qt, an initial Qt flavour of LXDE, and Razor-qt, a project aiming to develop a Qt based desktop environment.
More on this topic can be found in the Wiki.