USB Type-C Hub Mac recognises as display

please look around in there and find the NAME or resolution or anything you can find out about the "ghost display".

If it will not show you, use

 menu > about this Mac > (system Report) > Graphics&Displays:

.

if the display persists after a Restart, and can be "arranged" in the arrangement pane, then some software or hardware somewhere is creating a profile for a display that is not actually present.

The Mac uses a system that reminds me of “Plug and play” to determine what "real" displays are connected, and what its capabilities are.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. 

There are additional ways you can set up a "fake" display profile, like DisplayLink as I mentioned. Then no actual query would be sent, because the information would already be available. This is the approach used for the built-in display -- no query is actually sent.

If you wanted to do that for some reason, apps like SwitchResX and similar would be used.

¿have you ever used such a program to manually adjust display capabilities?

To see whether the Satechi adapter is answering the Mac's query and thereby manufacturing this display, you can test by removing the adapter and checking to see whether the "ghost" display is still present after a Restart.

Then the "ghost" display appears to be 'manufactured' by the Satechi adapter, or any software that goes along with the adapter.

maybe their tech support has some additional advice.

my first inclination is to assume you were running a "fake" DisplayLink display. But Satechi is not shown as a maker of DisplayLink adapters.

¿did you ever use a displayLink dock/adapter?

perhaps the adapter has failed.

You have exactly ONE cable from the Satechi adapter to the display, not two, right?