nouveau error message appears on boot after upgrading nvidia driver manually

My Linux PC has a Nvidia GPU. I used to manage the graphics driver by the

-driver

package. However the stock is a bit behind so I decided to install the latest one myself from Nvidia. I made the script executable.

chmod +x NVIDIA-Linux-x86_64-535.98.run

I ran the script but I get an error.

NVIDIA-Linux-x86_64-535.98.run
ERROR: An NVIDIA kernel module 'nvidia-uvm' appears to already be loaded in your kernel. This may be because it is in use (for example, by an X server, a CUDA program, or the NVIDIA Persistence Daemon), but this may also happen if your kernel was configured without support for module unloading.  Please be sure to exit any programs that may be using the GPU(s) before attempting to upgrade your driver.  If no GPU-based programs are running, you know that your kernel supports module unloading, and you still receive this message, then an error may have occurred that has corrupted an NVIDIA kernel module's usage count, for which the simplest remedy is to reboot your computer.

I pressed ctrl+alt+f2 to switch to tty then logged in as root. Then I disabled the GUI and unloaded

-drm

.

systemctl isolate multi-user.target
modprobe -r nvidia-drm

I ran the script the second time but this time I got a message telling me that nvidia debian packages are not compatible with this method and thus should be uninstalled first. So I removed the nvidia debian packages to prevent conflicts.

sudo apt purge nvidia*

I ran the script again.

NVIDIA-Linux-x86_64-535.98.run

Now the script runs fine. I then rebooted to see whether it worked.

reboot

It booted to GUI just fine but during booting I saw an error message:

nouveau 0000:08:00.0: unknown chipset

I checked which driver was running and confirmed that the newly installed nvidia driver is running.

lshw -c video
  *-display                 
       description: VGA compatible controller
       product: GA102 [GeForce RTX 3080]
       vendor: NVIDIA Corporation
       physical id: 0
       bus info: pci@0000:08:00.0
       ...

Why is nouveau loaded during boot although I never activated it? How can I have the message not show up?