I’m not sure. I have an Xfce install that is EndeavourOS theme and Nvidia GTX 1060. I had no issues with updating to the new mesa. Do you have your Nvidia set up with the additional enhancements as per the wiki?
Edit: https://discovery.endeavouros.com/nvidia/nvidia-optional-enhancements-and-troubleshooting/2021/03/
After getting responses from @MrToddarama and @ExDebianuser that they did not experience this problem while using GDM, I switched from LightDM to GDM. With GDM everything boots up and works fine with mesa 21.0.1-1
At this point, I’m not sure if the problem is mesa or lightdm or a combination of the two.
Pudge
No joy … GDM Still doesn’t start. I skipped the first enhancement (since it basically says ‘this can break GDM’), but I did implement the early module load and screen tearing enhancements. There are still issues that keep gdm from starting with version 21.0.1-1 of the mesa packages. Rolling back to 20.3.4-3 mesa packages fixes the issue.
I didn’t set up like that…
I disabled the intel video card inside the BIOS…
Regarding the screen tearing, I was setting my monitor refresh rate to 144hz, and no more screen tearing…
Edit: Forgot to mention, using a GTX 1660 video card.
Well @Pudge switched to GDM and his boots up fine. So this is strange as I’m using lightdm and Nvidia and have no issue. I do have mine set up with the enhancements.
I have and ASUS Zenbook Flip with the specs listed below
~ >>> inxi -G
Graphics:
Device-1: Intel UHD Graphics 620 driver: i915 v: kernel
Device-2: NVIDIA GP108M [GeForce MX150] driver: nvidia v: 460.67
Device-3: IMC Networks USB2.0 HD UVC WebCam type: USB driver: uvcvideo
Display: wayland server: X.Org 1.21.1 driver: loaded: modesetting
unloaded: nvidia resolution: 1920x1080~60Hz
OpenGL: renderer: Mesa Intel UHD Graphics 620 (KBL GT2) v: 4.6 Mesa 21.0.1
where I am running my locally compiled copy of gdm-prime with gnome 40 and I don’t have any issue. it’s only on older Sager notebook where I am seeing the issue. I guess I’ll wait for another mesa version to see if it resolves. Too busy working to pay the bills and not enough time to dig into trying to troubleshoot.
Actions taken:
1- Boot live USB from EOS, ran the install, removed and recreated the partitions.
2 - Installed the system again, XFCE, online install.
3 - After the install, rebooted the system and confirmed that mesa 21 is installed.
4 - Ran sudo nvidia-installer-dkms and rebooted.
This time, the problem happened with the vanilla XFCE theme…
So, now I’m suspecting of a conflict between mesa 21 and nvidia driver.
Edit: I’ll try now using the enhancements suggested by ricklinux in a previous post.
Updates soon.
1- Boot live USB from EOS, ran the install, removed and recreated the partitions.
2 - Installed the system again, XFCE, online install.
3 - After the install, rebooted the system and confirmed that mesa 21 is installed.
4 - Ran sudo nvidia-installer-dkms and didn’t reboot.
5 - Performed all the steps found in the wiki page https://discovery.endeavouros.com/nvidia/nvidia-optional-enhancements-and-troubleshooting/2021/03/
Everything is working perfectly now, mesa21, XFCE lightdm, and nvidia driver
It seems that the driver needs to run earlier KMS, as per wiki page mentioned above, suggested by ricklinux.
I failed to mention that I’m using a Desktop with 2 GTX 1070–no changes to anything Nvidia (no enhancements)–running the current mesa without problems.
2 GTX 1070? No enhancement needed. 
Well–As SLI works like you know what in Linux …One card is for the screen & then both get used for BOINC in times I’m not using the computer…my bit for science.
Thank you guys!
I had the same issue (hang after login) after an update on the weekend.
Executing the first two steps under @ricklinux’s link solved it for me. 
(I didn’t have any screen tearing issues before, so I didn’t execute the enhancement step).
after some updates earlier this year this issue start popping up, as usually, Nvidia should start early in boot process on its own, it needs to force that early boot.
On Lightdm: it is a good idea to enable lightdm.conf to logind-check-graphical=true what prevents lightdm from starting earlier then GPU is fully initialized.
// we will set this per default in future release maybe //
Just did it.
Now with the nvidia enhancements and with lightdm logind-check-graphical=true, I doubt that this problem will ever happen again.
Thanks everyone for the help
I have also made this additional change on my Nvidia system. I have also noticed with some updates that the mkinitcpio .conf file reverted the modules setting from “nvidia” back to modules="". So i am keeping an eye on this in future updates to see if it happens ever again.
Got my Sager NP8568 and GTX980M card working again. He already set up the early load of nvidia module and still had issues. Removed all of the nvidia drivers and reinstalled them again … now it works with latest mesa-21.0.1-1 … I’ll probably never know what config file or other random setting I messed up that we then corrected by removing and reinstalling.
I think it will may happen again with updates. The advanced configuration and enhancements seem to help from that happening for the two systems i look at here. So far i have been good for a while now.
Probably redoing the mkinitcpio has same effect my 2 cents. Reinstalling does not change to much but recompiling initram can have some effects.
I think you are right on this as that is what i did the last time i had an issue with the Nvidia.
@joekamprad
Okay so i added the logind-check-graphical=true to the lightdm.conf and low and behold lightdm fails to start. So i changed it back to commenting it out. Now i update the kernel. I still have all the other additional enhancements.
Edit: So for me the lightdm setting actually causes it to not work. Kernel is loaded and all is good!
[ricklinux@eos-xfce ~]$ uname -a
Linux eos-xfce 5.11.11-arch1-1 #1 SMP PREEMPT Tue, 30 Mar 2021 14:10:17 +0000 x86_64 GNU/Linux
[ricklinux@eos-xfce ~]$
Edit2:
[ricklinux@eos-xfce ~]$ inxi -Ga
Graphics: Device-1: NVIDIA GP104 [GeForce GTX 1060 6GB] vendor: ASUSTeK driver: nvidia
v: 460.67 alternate: nouveau,nvidia_drm bus ID: 01:00.0 chip ID: 10de:1b83
class ID: 0300
Display: x11 server: X.Org 1.20.10 driver: loaded: nvidia display ID: :0.0 screens: 1
Screen-1: 0 s-res: 1920x1080 s-dpi: 96 s-size: 508x286mm (20.0x11.3")
s-diag: 583mm (23")
Monitor-1: DVI-D-0 res: 1920x1080 hz: 60 dpi: 102 size: 477x268mm (18.8x10.6")
diag: 547mm (21.5")
OpenGL: renderer: GeForce GTX 1060 6GB/PCIe/SSE2 v: 4.6.0 NVIDIA 460.67
direct render: Yes
[ricklinux@eos-xfce ~]$