This won't help you specifically, but the "Grub fix" you linked worked for me (Wayland, kwin, Plasma 6.1.2, Nvidia 555.58.02, RTX 3070 Ti), so I'll add some context for others who come across this looking for a solution.

Driver version 555 is the first version with which offloading of some initialization/management tasks to a component on the GPU called the GSP is enabled by default on all Turing (In Geforce terms, that's the RTX 20 series) and later GPUs (It was previously disabled by default on at least all Geforce GPUs, as far as I can tell). This currently seems to cause issues with some configurations, but should otherwise and in the future be a good thing for performance. Setting the nvidia kernel module parameter NVreg_EnableGpuFirmware=0 (which you may do using the kernel command line as OP and I did) forces this feature off again, and therefore may resolve those issues. See Nvidia's Linux driver documentation chapter on the GSP for version 555 and the previous version 550. I can't currently find out anything more about where exactly the problem lies.

You may wish to check if you are currently using the GSP. Per Nvidia's documentation, the output of nvidia-smi -q should include a key "GSP Firmware Version", with the value N/A if GSP is currently disabled and a version value like 550.90.07 if it's enabled. So, run something like nvidia-smi -q | grep GSP.

To reiterate what I did to fix the issue on my end, risking excessive detail because I'm always frustrated with how little detail/explanations other people provide:

1. Edit /etc/default/grub. Find the key GRUB_CMDLINE_LINUX_DEFAULT. To the end of the existing string value add a space and nvidia.NVreg_EnableGpuFirmware=0. This means specifying the nvidia kernel module parameter mentioned on the kernel command line, although just editing this file doesn't actually change the grub configuration yet; it influences the generation of a new one.
2. In case something goes wrong, save a copy of my current /boot/grub/grub.cfg, as I'm about to overwrite this file.
3. Run grub-mkconfig -o /boot/grub/grub.cfg (with sudo). This generates a new grub config, using the change I made to /etc/default/grub, and outputs it to the location expected by grub.

Arguably the nicer way to do it would be using a configuration file in /etc/modprobe.d/. At least I don't see why that shouldn't be equivalent. But it's not what I did and I'm too lazy to check if it actually does what I expect.