Apple.

Apple has posted a support document addressing an issue that may occur with the 14- and 16-inch MacBook Pro with a Liquid Retina XDR display or Apple’s Pro Display XDR. Apparently, those displays can start to warm up if the brightness is high for an extended period and the room is hot, sending them into low power mode and brightness limits kick in. .

If you see the symbols at the left in the menu bar or in Control Center’s Display’s menu, your display is in low power mode.
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