Monitor Turns Black after Booting Ubuntu 20.04.5 LTS

We use GPU: RTX A4500, Driver: 515.105.01, OS: Ubuntu 20.04.5 LTS. When the system starts to boot BIOS, the monitor showed video output from Display Port of A4500, i.e. the progress of BIOS booting. After booting Ubuntu 20.04, the monitor screen turned black and hang. Unplugged the DP cable, and switched to a VGA cable to connect the Monitor to the VGA port on the motherboard, the monitor showed video output. We tried 4 A4500 GPUs, all showed the same phenomenon. It’s repeatable. Would appreciate any insights on this issue.