OK, I posted too soon. 
I looked at the Debian website & found a simpler .xinitrc (more like I remember from the old days) than what I read on the Archwiki. So, based on that, I modified it & a couple of boots later I now have success! 
So I can continue solving the long list of problems that I’ll strike as my new EndeavourOS system evolves into what I desire it to be.
For anyone interested in not using a GDM to start their WM/DE, then a good place to start is by making something like the following ~/.xinitrc & then customising from there. (Well, it worked for me.)
You’ll also have to turn off or uninstall the GDM that you are using.
#!/bin/sh
# ~/.xinitrc
# This file is sourced when running startx and
# other programs which call xinit
# As in all Bash/sh scripts lines starting with
# '#' are comments
# Always put a '&' at the end of every line but the last.
# as this runs things in the background.
# Also, make sure to make the file executable &
# I stuck the first line in this file #!/bin/sh as Debian didn't.
# Set background to your favorite pic
##xsetbg -fullscreen /morphix/background.png &
# Start a XTerm
/usr/bin/X11/xterm &
# Start the systems window manager.
# I used openbox like so:
exec openbox-session
# To run xfce4 instead of system default, place a
# '#' before the previous line and uncomment the
# next line.
# exec xfce4-sessionAnyway, I’ll mark this one solved.