RE: Dell U2417H displayport daisy chain mirrors, but does not extend.
Not sure what else you can do but test them on another system with a dedicated video card that has DP or mDP and also testing with a DP to DP cable on that HP. Where did you find HP documentation that stated its onboard DP out port supports DP 1.2 daisychaining? That is not mentioned here or here ?
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Run the PC pre-Windows diagnostics
Where do I find my Dell PC Service Tag or Express service code?
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