this is the only message related to lightdm:
lightdm[2162]: gkr-pam: unable to locate daemon control file
and if you enter tty and type: startx can you log in?
post output from:
cat /usr/lib/systemd/user/gnome-keyring-daemon.service
I installed 470xx again, and then the optimus/manager using the GUI. The “systenctl enable…” did not give any response (it seems the cmd just hang: neither did I get a new line, nor was there an error.
I edited the grub anyway: please confirm that I did the right thing here:
I entered the two remaining commands and rebootet. I do not get the lightdm error, but I do not get to the GUI. After selecting the 5.19 kernel, I just see a output about my ssd (clean blocks).
Entering the tty and startx leads to the fatal error “no screen detected” I posted.
so edit the file:
sudo nano /usr/lib/systemd/user/gnome-keyring-daemon.service
and edit this line:
WantedBy=default.target
to look like this:
WantedBy=graphical-session.target
save it with ctrl+x
reboot
also uninstall the optimus and remove the kernel parameters before you reboot
All done. Afterwards I installed the 470xx version. Reboot leads to the same lightdm-error. 
did you install optimus-manager? i doubt.
check also this:
cat /usr/lib/systemd/user/gnome-keyring-daemon.socket
and if the WantedBy looks like this:
WantedBy=sockets.target
if no edit it like you did before, reboot
if it looks like it, then thats all from me, except to use the gdm as is suggested above
yes, in the gnome/keyring/daemon.socket it says “WantedBy=sockets.target”.
I really appreaciate that you spent so much time on this, brahma. Thank you.
yes, I did. I followed your instructions which led to no output on the screen after the reboot. In more detail, I select the kernel when booting and the only thing that follows is a line about my ssd-drive and its blocks.
Following brahma’s instructions, I uninstalled the optimus-manager again, and removed the entries. Did you take a look at the image I posted? Were the entries ok?
also try this kernel parameter:
ibt=off
add into grub command line like you did with the nvidia parameters … you can add it in grub menu, press E and add that parameter there and see if it helped
I added “ibt=off” into /etc/default/grub,
at the end of the line GRUB_CDMLINE_LINUX_DEFAULT
No improvement.
so switch to the gdm
Installed and activated gdm following these instructions: Install Display Managers - Manjaro
Uninstalled nvidia driver. I get to the login-screen. After login, screen remains black.
of course it remains black, since you uninstallled nvidia drivers … you have only nvidia as a gpu …so install nvidia again
I tried with 470xx, and just now with the video-nvidia (2021.11.04). Before the login-screen, the boot process stops and shows a blinking cursor. I can use the tty though.
so it was not related to lightdm … post output from:
find $HOME/ -name ".Xauthority"
find /etc/X11/ -name "*.conf"
the 10-nvidia.conf was created by you?