Brightness Sync Yukhnevich
Install Brightness Sync with WinGet
winget install --id=Yukhnevich.BrightnessSync -e Windows stores display brightness separately for every power plan, so switching power modes (for example ASUS Armoury Crate Silent / Performance / Turbo) changes the brightness. Brightness Sync is a small tray utility that writes the current brightness into every power plan, so all modes share one brightness level. Scroll over the tray icon to change the brightness of the laptop and external monitors (over DDC/CI). All displays move together and keep the difference between them. In HDR, monitors get SDR content brightness, and the laptop keeps its usual brightness apart from HDR's.