startx gives black screen with nvidia drivers

Some info:

distro: lubuntu 20.04
default dm - sddm
gpu - integrated intel, and Nvidia GTX 1650 mobile
nvidia drivers - nvidia-470

When I use the default display manager provided sddm the system works perfectly fine i.e i3 openbox every wm works.

But as soon as I use startx /usr/bin/i3 i get a black screen, i also created .xinitrc still same result. I also use another wm like openbox, i.e. openbox-session still same result.

I stopped sddm service and tried startx again still same result, i get black screen with no cursor. I switch to another tty and use htop and i can find that both xorg and i3 are running.

I checked the xorg log and it reports no error. prime-select query gives nvidia as result. If I use prime-select intel and then reboot the startx works. So I think I have to configure something when using nvidia.

How can I make startx work so I don't get a black screen ?

Thanks. If I should add some more information please tell I will add it.

htop preview of sddm

├─ /usr/bin/sddm
│  ├─ /usr/lib/x86_64-linux-gnu/sddm/sddm-helper --socket /tmp/sddm-auth1a548eff-e892-4543-89ec-705e1c6138a1 --id 1 --start i3 --user totoro
│  │  └─ i3
│  │     └─ /usr/bin/ssh-agent i3
│  ├─ /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{36771d4e-9416-4be0-bfae-49c50dc60bc3} -background none -noreset -displayfd 17 -seat seat0 vt1
│  │  ├─ /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{36771d4e-9416-4be0-bfae-49c50dc60bc3} -background none -noreset -displayfd 17 -seat seat0 vt1
│  │  ├─ /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{36771d4e-9416-4be0-bfae-49c50dc60bc3} -background none -noreset -displayfd 17 -seat seat0 vt1
│  │  ├─ /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{36771d4e-9416-4be0-bfae-49c50dc60bc3} -background none -noreset -displayfd 17 -seat seat0 vt1
│  │  ├─ /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{36771d4e-9416-4be0-bfae-49c50dc60bc3} -background none -noreset -displayfd 17 -seat seat0 vt1
│  │  └─ /usr/lib/xorg/Xorg -nolisten tcp -auth /var/run/sddm/{36771d4e-9416-4be0-bfae-49c50dc60bc3} -background none -noreset -displayfd 17 -seat seat0 vt1
│  └─ /usr/bin/sddm

htop preview of startx

├─ /bin/login -p --
│  └─ -zsh
│     └─ /bin/sh /usr/bin/startx
│        └─ xinit /home/totoro/.xinitrc -- /etc/X11/xinit/xserverrc :1 vt2 -keeptty -auth /tmp/serverauth.czCRUMFwtc
│           ├─ /usr/bin/openbox --startup /usr/lib/x86_64-linux-gnu/openbox-autostart OPENBOX
│           └─ /usr/lib/xorg/Xorg -nolisten tcp :1 vt2 -keeptty -auth /tmp/serverauth.czCRUMFwtc
│              ├─ /usr/lib/xorg/Xorg -nolisten tcp :1 vt2 -keeptty -auth /tmp/serverauth.czCRUMFwtc
│              ├─ /usr/lib/xorg/Xorg -nolisten tcp :1 vt2 -keeptty -auth /tmp/serverauth.czCRUMFwtc
│              ├─ /usr/lib/xorg/Xorg -nolisten tcp :1 vt2 -keeptty -auth /tmp/serverauth.czCRUMFwtc
│              ├─ /usr/lib/xorg/Xorg -nolisten tcp :1 vt2 -keeptty -auth /tmp/serverauth.czCRUMFwtc
│              └─ /usr/lib/xorg/Xorg -nolisten tcp :1 vt2 -keeptty -auth /tmp/serverauth.czCRUMFwtc

Since I'm using nvidia-prime, I have to add some lines in the .xinitrc for it to work. The display manager sddm does it too but I don't know where it's script is.

Add these lines to starting of .xinitrc

xrandr --setprovideroutputsource modesetting NVIDIA-0
xrandr --auto

Source - NVIDIA-Optimus ArchWiki

Even better add some if,

DRIVER="$(prime-select query)"
if [ "$DRIVER" = 'nvidia' ]; then
    xrandr --setprovideroutputsource modesetting NVIDIA-0
    xrandr --auto
fi