Samsung M8 and mac mini cant adjust brightness

Your Samsung monitor includes an on-screen display menu, or OSD, for adjusting the monitor's brightness, contrast, color, size and skew. These settings adjust the display to suit your personal preferences or the brightness of your work environment. Optimally adjusting the OSD settings makes the screen easier to see and may reduce eye strain when working long hours in your business. The Samsung OSD resides within the monitor itself, so it functions independently of the operating system and does not require additional software.

1. Connect the Samsung monitor to your computer and power on both devices. Although it is not vital to connect a video source, it helps you properly adjust the monitor when your typical work display is on-screen while making adjustments.
2. Press the "Menu" button on the monitor to bring up the OSD. Alternatively, press the arrow buttons on many Samsung monitors to directly access some features, such as brightness or MagicBright controls.
3. Press the arrow keys to highlight a tab and press the "Select" button to access adjustments on that tab.
4. Press the arrow keys again to highlight a specific option, such as brightness or contrast, and press "Select."
5. Press the arrow keys to make adjustments to the selected option.
6. Press "Menu" again to exit the OSD. Alternatively, wait several seconds without pressing buttons for the menu to automatically close.

https://smallbusiness.chron.com/adjust-samsung-monitor-screen-55842.html

Here is how to generally change the brightness on your Mac:

Change your Mac display’s brightness – Apple Support

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