Custom Resolution Utility (CRU)

[olco]

I got a new 2020 Huawei Matebook D14 (R5 3500U) and tried to connect it to my Iiyama ProLite XUB3490WQSU-B1.

The Matebook's HDMI output is specified as 2.0b. The Iiyama got HDMI 2.0 and DP 1.2 inputs.

Recently the Iiyama was connected via HDMI to my desktop pc (980ti) which worked fine at 3440x1440@60Hz.
It also works via a DP cable, to which connection I switched for now.

So the problem is, I can only get 3440x1440@30Hz via the Matebook. As the USB-C port of the 2020 version doesn't seem to support DP alternate mode which the 2019 version did, I have to connect it via HDMI.

I am using the same input of the monitor and the same cable which works for my desktop pc, but I only get 30Hz.

So I tried to get it to work using the CRU but wasn't successful.
Is it important for the monitor to get listed as the correct monitor model instead of "PnP-Monitor"?
If I try to set 3440x1440@60Hz via the radeon software (Adrenalin 2020 Edition 20.4.2 from 23.04.2020) as custom resolution the software tells me that the resolution wasn't compatible with that monitor.

Do you have any hints for me, how to get the 60Hz out of the Matebook?