display – Sleep broken on a late 2021 MacBook Pro M1 when connected to external hdmi monitor

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Using macOS 12.2.1 on a MacBook Pro M1 while connected to an external monitor breaks sleep mode. On Linux / Windows I expect the sleep mode to power off both my laptop screen and my external monitor by default (plus setting the device into sleep mode).


With this Mac, however, either closing the lid or manually selecting “Sleep” while connected via HDMI to the external Monitor prevents the device to actually switch modes.

Even more, when closing the lid I can still use the mouse and keyboard on the external display, which is not only annoying but also when in an office can lead to privacy issues. The device is not automatically locked after closing the lid and having the monitor connected.

So far the only solutions I've found are:

  • shutting down the device
  • disconnecting from the external monitor before closing the lid / going to sleep mode
    None of them are ideal, so I'm wondering if someone run into the same issue and found a solution.

The monitor is a LG 27UK670, and I'm connecting to the right side HDMI port.

Author: Subham

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