My displayport monitor loses signal if I get to the login screen. I have autologin enabled, and the system boots fine. If I turn off autologin, I have to plug in and hdmi second monitor to get it to detect. I don’t routinely use my second monitor so this is a pain. If I logout once booted, the screen dies. I have a 1070 with the latest non-beta drivers on kde 5.22.5 X11, and using kernel 5.14.12. I don’t know how to even begin to troubleshoot this. I’m a relatively noobish in linux.
/usr/share/sddm/scripts/Xsetup
with a xrandr script could do the trick, if your issue is that the dp display is your usually used display, it could be that sddm (login manager) does not detect it in a good way also you have set it up on DE correctly.
you can try using arandr (xrandr GUI) setup your display and save the settings as monitor, than paste the saved script into /usr/share/sddm/scripts/Xsetup (needs root permission)
And for sure welcome at the purple side 
Ok, I think you have an extra e in arandr? I used arandr and pasted
xrandr --output DVI-D-0 --off --output HDMI-0 --off --output DP-0 --off --output DP-1 --off --output DP-2 --primary --mode 2560x1440 --pos 0x0 --rotate normal --output DP-3 --off --output DP-4 --off --output DP-5 --off
into Xsetup, but it didn’t change anything.
Thank you
had that sry 
to get more research i would need some logs…