U3225QE, no signal from Thunderbolt when connecting a HP ZBook Power G8

I had exactly the same behavior as described here in this other issue with an Elitebook G8. - but with a different solution. Updating the HP drivers of the laptop didn't help. I had to update the firmware of the (brand new, just arrived) Dell U3225QE, using the "Dell Display and Peripheral Manager" to make it work. I used the USB-C-port in the back without power for the update process, while also being connected via HDMI cable. The HDMI cable was necessary for the program to recognize the screen. Now it works fine as docking station, finally with 120 Hz.

The firmware update should also fix the auto brightness adjustment issue - I will find out tomorrow.