Who uses DisplayLink to run the To expand Mac screen on a USB cable connected iPad, should not first play macOS 10.13.4th By the update, the screen output is no longer working as usual. This is due to unadapted drivers from the manufacturers, which is why the screen extension no longer works.
Other USB graphics solutions also fail to work - for example, connected displays that are powered by USB. Well-known solutions are Duet Display, Air Display and iDisplay. For example, the iOS app Duet Display can turn the iPad Pro into an external display for the Mac or PC that can control software like Photoshop, Lightroom, and Illustrator using Apple Pencil. Duet Display consists of two apps: one for Windows or MacOS, the other for iOS. Duet installs another display driver on the desktop operating systems, which transmits the image to the iPad via a lightning cable. Depending on the setting, frame rates of 30 and 60 frames per second are achieved.
According to DisplayLink Apple has already been informed about the circumstance. According to information from the manufacturer, there are already drivers in a beta version, which at least allow the clone mode again - but the screen does not expand yet.
The problem is that macOS 10.13.4 also numerous security-related fixes includes. Those who rely on the USB display solution are in a bind.