4K 60 Hz not working via AVR

I have a problem running LibreELEC 10.0.2 on the HTPC connected to my home cinema:

When connected via the AVR to the TV set, 4K 60 Hz is not available (30 Hz is the maximum). When connected directly to the TV set 4K 60 Hz is working fine.

My setup is as follows:

- LG OLED55C28LB

- Denon AVR X1700H

- AMD Ryzen 3 2200G on ASROCK B450 Fatal1ty

The cables are all HDMI 2.1 / Display Port 1.4, the HDMI ports on the AVR are all 2.1 as well. I tried HDMI settings 4K Enhanded and 8K Enhanced on the AVR and even switched to an 8K HDMI port on the AVR. Still 4K 60 Hz is not showing up.

I it to work connecting the HTPC directly to the TV set and running

getedid create

After reconnecting the HTPC to the ACR the 60 Hz modes were still available.