I know Deepin v20.9 doesn't go into standby or sleep after a period of inactivity, it just turns off the monitor. If you unplug the HDMI cable during this period, when you press a key to "wake" up the system, it assumes the HDMI display is still connected. As a result, you see nothing on the embedded display.
The only way to remedy is to plug the HDMI cable back in (after the system is "woken up") then unplug it to get the system to recognize yes the HDMI display is no longer connected (and switch to the embedded display), which is super-annoying.
中文 
Dependency error 
I know Deepin v20.9 doesn't go into standby or sleep after a period of inactivity, it just turns off the monitor. If you unplug the HDMI cable during this period, when you press a key to "wake" up the system, it assumes the HDMI display is still connected. As a result, you see nothing on the embedded display.
The only way to remedy is to plug the HDMI cable back in (after the system is "woken up") then unplug it to get the system to recognize yes the HDMI display is no longer connected (and switch to the embedded display), which is super-annoying.