I upgraded to Monterey 12.0.1. Release notes https://developer.apple.com/documentation/macos-release-notes/macos-12_0_1-release-notes say: 'There might be issues with wakeup when dual monitors are connected. (79839446). Workaround: Connect the power adapter that came with the Mac.'.
On Big Sur, my external monitors never worked without the laptop being connected to external power.
At work, I have two HDMI screens from Samsung connected to the USB-C port on my macBook through a Satechi hub. Both monitors are configured as Extended displays. The displays work unless I close the lid of the laptop. Then all go black.
At home, I have only one Samsung HDMI screen, configured to mirror the laptop. Here, I can work with closed lid. This monitor is also connected to a Satechi hub, but a different one as the one at work.
