Black screen when resuming systemctl-suspend, using nvidia-driver-470.57.02 with kernel 5.8.0-63-generic on GTX 970, xubuntu 20.04 LTS

Can you please check with driver 495.46 and confirm if it fixes issue on your setup.
If issue still persists, please share nvidia bug report from repro state and also confirm how are you doing suspend/resume on your system.