i915 nouveau Nvidia GPU not starting lightdm Xorg failing solution for Could not determine valid watermarks for inherited state
It may appear to be an Xorg or lightdm/gdm/mdm error but in reality for many users with this issue, it's a driver conflict and issue. I had a system that had two GPUs, an Intel and Nvidia GPU.
The only thing that got it working was to remove the nouveau driver and blacklist it so it never came back, then the Intel GPU works fine without these issues.
Solution
sudo rmmod nouveau
add nouveau/other driver to blacklist
edit th........
LightDM Mint Ubuntu Debian won't start errors Nvidia Graphics
This error implies that there may be an issue with Xorg or maybe your NVIDIA GPU cannot start or initialize:
35 laptop kernel: [ 2031.857704] nvidia: loading out-of-tree module taints kernel.
35 laptop kernel: [ 2031.857724] nvidia: module license 'NVIDIA' taints kernel.
35 laptop kernel: [ 2031.857725] Disabling lock debugging due to kernel taint
35 laptop kernel: [ 2031.873280] nvidia: module verification failed: signature a........