Why is my GPU malfunctioning during startup?

Question

This issue was previously posted on the Lubuntu subreddit, and the person who graciously spent time helping me figure it out told me to share it on here, because we ran out of ideas. I hope someone on here will have come across something like it before. Please check out the original thread with all the stuff we tried out.

What we ended up finding out is that the issue most likely stems from the GPU, but installing the additional drivers didn't fix anything. Another weird thing is that the GUI only rarely has issues beyond that. Here is a link to some logs showing what is going on: https://paste.ubuntu.com/p/hYhHxNGfXp/

Here is a description of the issue:

I set up Lubuntu 22.04.4 (the latest LTS build back when I did it) on my 2008 Unibody MacBook Pro, and I have a weird issue that I am struggling to figure out on my own.

The issue most likely doesn't stem from the quality of the download, as I spent a while figuring out whether my sha256sum hash was correct (see this post). I ended up using the ISO I got off zsync. Please do ask questions if you think it might come from there anyway.

Anytime I boot up Lubuntu, I end up with this or this. Notice how the cursor is displayed in the middle of the screen (it can't be moved). Sorry for the janky phone pictures of the screen, you'll understand I can't take screenshots. It turns out that when I get to that point, I can type out my password and log in. This hints at something being wrong with the login page (which I do sometimes see properly).

I also have an issue where I need to try a few times every time I boot up the laptop, because it simply freezes before getting to a point where I can log in. I think that's a separate issue so I might ask about it in a different post another time, but for all I know it could be related so I'm mentioning it here anyway.

Answer 1

The solution that eventually worked was as shown below. What made the difference is point 3, I only included the rest because it's unclear from the post itself what the final setup is.
1- Reinstalling Nouveau with
sudo apt install nouveau-firmware
2- Re-enabling the Additional Drivers;
3- Replacing the current display manager (SSDM) with XDM:
sudo apt install xdm
The terminal should automatically display a menu asking you which display manager to use, and you simply need to select XDM with the arrow keys and press the enter key.
4- Rebooting the computer.

Getting the Nvidia driver directly from their website did not work as it conflicts with Nouveau in a way that I could not figure out. If you let the Nvidia installer disable Nouveau, do:

rm /usr/lib/modprobe.d/nvidia-installer-disable-nouveau.conf
rm /etc/modprobe.d/nvidia-installer-disable-nouveau.conf

Amazingly, this seems to also have fixed the other issue I mentioned at the very end of my post.

Thank you to Mika Lindqvist and u/wxl on Reddit for the invaluable help!

Answer 2

The logs reveal several issues... There seems to be crashing bugs in at least two drivers, and the display manager doesn't support the current version of Qt library.

I would try different version of "nouveau" driver or falling back to standard VGA driver, if there isn't supported version for your graphics chip.

Out-of-bound access in the other driver needs more investigation from the kernel developers or the assigned maintainer of the respective driver. See the log line mentioning "bcmwl/6.30.223.271+bdcom".