Skimming off wireless electromagnetic signals for surveillance ... at least some level of encryption using the HDCP system, HDMI cables weren’t thought to be particularly susceptible to it.

A Miracast-based device from Microsoft that plugs into a TV, projector or monitor via HDMI and USB. Starting with Windows 8, the Wireless Display Adapter (WDA) lets a Miracast-enabled Windows PC ...

With wireless casting making its way to the market ... you can use a USB-C-to-HDMI adapter as a workaround. Though MHL works ...