The HDMI source port must be used to via corded connection. The USB-C port is designed to mount the R50 as a device drive to a computer for updates using Garmin Express as an alternate update method.
If you are using a wireless HDMI adapter, and if you find that adapter works for display extension or mirroring...an external power source for the USB-C should be used to test if the adapter will allow the use you are attempting for the HDMI connection.
