Not sure if you ever got this going or not, but here are my notes from my 20.04 rig
Install latest driver, reboot
Enable coolbits
sudo nvidia-xconfig --enable-all-gpus #use if running multi gpu
sudo nvidia-xconfig -a --cool-bits 28
Reboot
Then you can manually change fan speed and OC
If you want to load your OC at boot do the following
Create new file:
sudo gedit /home/your user name here/.config/autostart/gpuoc_all.desktop
In new window paste:
[Desktop Entry]
Type=Application
Exec=nvidia-settings -a GPUFanControlState=1 -a GPUTargetFanSpeed=75 -a GPUGraphicsClockOffset[4]=100 -a GPUMemoryTransferRateOffset[4]=500
X-GNOME-Autostart-enabled=true
Name=nvidia-fan-speed
Name[en_US]=gpuoc_all.desktop
Click Save, Reboot, Profit
Note: you can enter any filename.desktop that you want, enter in your own fan speed, clock and mem settings. This config will OC all GPUs with the same settings. This config is for RTX GPUs, if you are using GTX GPUs change the offset parameters from [4] to [3] like so
GPUGraphicsClockOffset[3]=100 -a GPUMemoryTransferRateOffset[3]=500
To edit the file afterwards
gedit admin:///home/your user name here/.config/autostart/gpuoc_all.desktop
If you want to use different OC and fan values for each GPU you would have to create a new file with the same info posted above for each GPU. Then you could name them GPU1.desktop GPU2.desktop etc