I am having similar problems and mine have not been resolved using any of the FAQ suggestions or suggestions in this forum post. I have a MacBook Pro (13-inch, 2017, Four Thunderbolt 3 Ports) with Catalina installed. I am running an Elgato Thunderbold 2 dock, with three Samsung monitors attached, one via a Kensington DisplayLink. I have managed to get rid of the black screen on the DisplayLink monitor, but now all it does is mirror the main monitor. I cannot get it to run in extended mode, as it did before the Catalina upgrade.
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