You may encounter an intermittent Flickering when you connect an Apple USB-C Digital AV Multiport adapter to an HDMI cable connection to a Dell flat panel display.
This appears to be a limitation of the Digital AV Multiport adapter.
This issue has not been reported on HDMI connections where the USB-C digital AV Multiport adapter was not used or Direct HDMI and DisplayPort connections.
If you must use a system with a USB Type-C port to connect to a Dell Monitor, Dell Technologies recommends a basic USB Type-C to HDMI cable adapter (See Figure 1).
Figure 1 - USB Type-C to HDMI Adapter Dell Part number 47KD7
With this adapter (USB Type-C to HDMI adapter Dell Part number: 47KD7), Dell monitors display video as designed. If your display came with a USB Type-C adapter, use that adapter. Otherwise, you can purchase this adapter from Dell.