Monitor problems with Macbook 12" & DELL U2518D

Hi there

i got a DELL U2518D 25" monitor which i want to use it with my Macbook 2017 12" on HDMI to HDMI with the original MAC USB-C to HDMI adapter.
Unfortunately it seems that this hardware combination doesnt work properly in the standard resolution 2560x1440 60 Hertz.

Error: The display changes to black every 5 seconds.

I had the previous version of this monitor and it worked very well. It is also the best business monitor price/value in my opinion. Unfortunately the previous model is EOL and not available anymore.

The DELL support is not at all helping: "We don't test on MAC, please buy another monitor" Aha?

The HDMI on the Macbook is a given as this is the only possible monitor connectivity, the monitor supports HDMI, DP and mDP.

I tried cables: HDMI <> HDMI, DP <> HDMI, mDP <> HDMI, none are working. I guess these cables are meant to work from DP to HDMI to connect a TV and not vice versa from HDMI (source) to DP (monitor).

I got it to work now on 1080p but this is not the native resolution and looks blurry.

Any thoughts how to resolve this task? I can imagine trying a USB-C to DP cable, but then I would need to change to MacBook Pro 😉

Thx