Question about LG 27ud58-B

Nein, du musst in den PS Einstellungen aktivieren.
https://www.playstation.com/de-ch...

Funktioniert, oder?

So the HDMI connections on the monitor are 2.0, that can't be the problem. Can you post exactly which cable you are using? I'm pretty sure it's the cable, anything else doesn't make sense.

No, unfortunately that does not work. The problem is that I can only select up to 1080 in the "Resolution" menu. The other two entries are deactivated.
I use a current premium HDMI cable from Vivanco.
As if the monitor is not recognised as 4K.

Here you will find a detailed explanation of how this works. https://www.playstation.com/de-ch...
Please also note that you need an HDMI 2.0 cable (HDMI 1.4 also works in some cases). I would also check whether your monitor has an HDMI 2.0 port at all or whether the HDMI connection is HDMI 1.3 or lower, because then it won't work either.