HDMI Extender with Ubuntu has Colour Problem - Other OS works fine

[timbergetter2]

I have installed a Mini HDMI Cat5e/6 Extender (Digitech AC-1726) onto my Ubuntu 22.04 LTS system to allow a second monitor to be operated in the next room. Everything is working except that there is now a very pronounced colour cast (magenta) on the second monitor. This colour cast is not present when a HDMI cable is used instead of the extender ethernet cable. I get the same problem if I use another Ubuntu computer or if I swap the monitors around or if I use other ethernet cables. Using just one monitor with the extender also causes the problem.

To troubleshoot this problem further I installed Windows 11 on the computer and the colour cast disappears and extender seems to work perfectly. I then installed Pop!_OS (an Ubuntu derivative) on to the computer and again, the colour cast disappears and extender seems to work perfectly.

I even tried a third instance of Ubuntu residing on a USB thumb drive and again I get the colour cast when I use the extender. What could there be about Ubuntu that causes the colour cast when an extender is used, but when Windows 11 or Pop!_OS is used there is no problem?

[timbergetter2]

I have also posted this question here https://askubuntu.com/questions/1481...-os-works-fine and further discussion is evolving there. If you would like to comment, would you kindly do that on the AskUbuntu forum.

[HermanAB]

There is a serial line protocol running over HDMI between the computer and the screen to configure things. With bad cables, things can go wrong. You can try to reset it with xrandr - assuming that you are using X.