MacBook Pro change contrast of external monitor

[sy-kalhor]

Hi all,

I have a MacBook Pro 2015 with a mac 27" external LCD (thunderbolt)

I had Kubuntu 19.04 installed and In Kubuntu I when I tried the F1 and F2 function keys to increase/decrease brightness it was working for both monitors as expected.

But Now I have switched to "ubuntu-desktop" but the brightness control onlu works for the built-in display of the laptop...I can not control the brightness of the external monitor anymore and it stays on 100% brightness and almost makes me blind Is there anything I can do to change the brightness of the external monitor?

[howefield]

Thread moved to the "Apple Hardware Users" forum.