habe das Problem gefunden.. liegt wohl an der Kombi UHD 630 + HDMI
Link
I tested the following options:
- Mac Mini 2018 via HDMI: does not work
- Mac Mini 2018 via USB-C to HDMI adapter: works (see note)
- Mac mini 2018 via USB-Type-C to DisplayPort adapter: works
- Mac mini 2018 via USB-Type-C (connected to a USB-C monitor): works
- Mac Mini 2018 + eGPU (Radeon RX 570) via HDMI: works
- Mac Mini 2018 + eGPU (Radeon RX 570) via DisplayPort: works
Summary: The Intel UHD 630 via native HDMI seems to be unsupported on Mac Mini 2018.