Lubuntu
Lubuntu is a fast and lightweight operating system with a clean and easy-to-use user interface. It is a Linux system, that uses the minimal desktop LXDE/LXQT.
What is Lubuntu?
Lubuntu is a faster, more lightweight and energy saving variant of 
Ubuntu using 
LXDE (for version 18.04 and earlier releases), the lightweight 
X11 Desktop Environment.
On October 18, 2018 Lubuntu announced the 18.10 Cosmic Cuttlefish release, which uses
LXQt as its base desktop environment that will be default DE for future releases too.
Ubuntu using 
LXDE (for version 18.04 and earlier releases), the lightweight 
X11 Desktop Environment.On October 18, 2018 Lubuntu announced the 18.10 Cosmic Cuttlefish release, which uses
LXQt as its base desktop environment that will be default DE for future releases too.
Easy to use and runs smoothly even on very old hardware and minimal RAM.
I enjoy Lubuntu very much, they did a good job with it. Its lightweight and fast. Its snappy and good enough to be a main OS, the bugs I experienced seem to be fixed but there are still some.
It's my go to Linux system for new and old hardware. No junk, super fast.
Before 18.04 lubuntu useing lxde and very very lightweight but now useing KDE plasma stuff and LXQt. Not lightweight than LXDE but still not bad and more modern look.
Very light weight awesome for raspberry pi etc... devices
I'm dual-booting this with Win7. It installed wonderfully on my Samsung NC110, didn't have to fix a single thing. It's fast and beautiful. Love it!