MicroXWin
Mir
Y Window System
DirectFB
Wayland
Xynth Window System
Metisse
XQuartz
Openbox
i3
Fluxbox
awesome
IceWM
dwm
Hyprland
Xmonad
Mir - The purpose of Mir is to enable the development of user interfaces shells.
i3 - A dynamic tiling window manager designed for X11, inspired by wmii, and written in C.
Y Window System - Y Window System is a platform that allows you to improve the speed, working, and efficiency of the application in your operating system and helps you to increase the responsiveness of applications similar to any locally based app.
Fluxbox - Fluxbox is a window manager for X that was based on the Blackbox 0.61.1 code.
DirectFB - DirectFB is a web-based platform that provides you with complete access to a software library that you can use for the acceleration of graphics, handling the input devices, and others for your Linux operating systems.
awesome - A dynamic window manager for the X Window System developed in the C and Lua programming languages.