External monitor lead to screensaver in-out loop

Question

Normal behavior:

After 1min of beeing IDLE, my laptop will show a blank screen to save power (not "suspend", just blank screen ) When the mouse is touched, the screen is back to life.

Abnormal behavior:

However, when my external monitor is plugged via a USB to HDMI adapter, this does not work correctly:

• After 1min of IDLE, the computer screen goes black,
• the external monitor detect the blank image, and after 2 min the monitor goes to IDLE mode,and this change of state wakes up the computer :/
• After 1 min IDLE, the computer screen goes black,and the loop continue .

I guess it an issue with my USB to HDMI adapter. Is there a way to fix it in software ? (aka blacklist this device from waking up the computer ? )

OS:

ubuntu 20.04 on a thinkpad t14s

Answer 1

It was an issue with my cheap USB-C to HDMI adapter. Changed it, now solved.

^{Answer from OP's comment.}