It is X Window System / X11 server for Android. X11 servers are generally more faster when compared to VNC but XSDL lacks the beautiful UI which VNC Viewer has. It comes to your choice and what suits you the most amongst VNC and XSDL.
Download and install XSDL app from Play Store
Open XSDL and wait until you see something similar to the screenshot below
Now start OS and type the command inside Linux :
export DISPLAY=127.0.0.1:0 && bash ~/.vnc/xstartup &
If you are of wifi network and want to access XSDL from another Android device then change the command to :
export DISPLAY=192.168.0.100:0 && bash ~/.vnc/xstartup &