Dell U3821DW 37.5" 21:9 Curved IPS Monitor (Silver) - Manual (Page 65)

Operating the monitor
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Setting the KVM switch
The built-in KVM switch allows you to control up to 2 computers from a single set of
keyboard and mouse connected to the monitor.
a. When connecting HDMI + USB-B to computer 1 and DP + USB-C to
computer 2:
NOTE: The USB Type-C connection currently supports only data
transfer.
Make sure USB for HDMI is assigned to USB-B and DP is assigned to
USB-C 90W .