xinit/xinit-xinitrc

#!/bin/sh
#
# ~/.xinitrc
#
# Executed by startx (run your window manager from here)

if [ -d /etc/X11/xinit/xinitrc.d ]; then
  for f in /etc/X11/xinit/xinitrc.d/*; do
    [ -x "$f" ] && . "$f"
  done
  unset f
fi

case $1 in
    gnome) exec gnome-session;;
    kde) exec startplasma-x11;;
    lxqt) exec startlxqt;;
    lxde) exec startlxde;;
    xfce) exec startxfce4;;
    *) for s in startlxqt startplasma-x11 gnome-session startlxde startxfce4; do
          e=$(which $s)
          if [ "$e" -a -x $e ]; then
             exec $e
             break
          fi
       done ;;
esac