Remote Mouse - Turn your smartphone into a wireless touchpad and keyboard now!
Xfce - Xfce is a lightweight desktop environment for UNIX-like operating systems. It aims to be fast and low on system resources, while still being visually appealing and user friendly.
KDE Connect - Integrate Android with the KDE Desktop
KDE Plasma Desktop - Plasma Workspaces is the umbrella term for all graphical environments provided by KDE.
Monect - Make the best use of sensors on smart device to control PC, simulate steering wheel, game-pad...
LXDE - Why will you like it? Less resource needs. You can use it on your less-pricey embedded board or salvaged computer. Component-based design. Don't want something in LXDE, or you don't want to use LXDE but only part of it?