Motherboard firmware might have updates. If you update, make sure it is exactly for your motherboard, otherwise you may brick the board.
You have only Intel graphics. Often package xf86-video-intel is not needed for newer machines, but that’s not always the case. So either install it and reboot, or uninstall it and reboot. See if either helps.
Changing the display manager might help. For example, if you have lightdm, try sddm.
Changing the display manager:
sudo pacman -Syu --needed sddm # the new display manager here
sudo systemctl disable lightdm # the current display manager here
sudo systemctl enable sddm # the new display manager here
The new iso should not be a problem. However, we saw a lot of problems with grub update couple of weeks ago. It is necessary to run the command before rebooting, else necessitates a chroot and fix it there.
This explains the fix. Still surprised in your case, I did not have any problems with updates and reboot with new iso…
Also see some blacklisting of Nvidia, did you do that? Or was that automatic install.
Also your boot parameter is entirely different than mine. Perhaps try install first without encryption, or if you do run the grub-install before reboot but right after update if you can. Curious if it is really grub related.
[ 6.579] (EE) AIGLX error: dlopen of /usr/lib/dri/i965_dri.so failed (/usr/lib/dri/i965_dri.so: cannot open shared object file: No such file or directory)
[ 6.579] (EE) AIGLX error: unable to load driver i965