Dell cannot speak to the non-validated Apple proprietary hardware, operating system, and drivers. You should ask the Apple users on their Forum for troubleshooting opinions. We only tested Windows computers on the U3818DW.
In theory, the U3818DW USB 3.0 Upstream Cable should be connected directly to a computers USB 3.0 port. Then, the U3818DW two side and two bottom USB 3.0 Downstream ports would achieve 5 Gbps data rate. See page 20 in the User's Guide =
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Dell Monitor Service Tag number, 20 digit S/N, A0x revision
Dell PC Service Tag number
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