SqlSetup: Incorrect calculation logic for xSQLServerMaxDop

Details of the scenario you tried and the problem that is occurring:
In the Get-SqlDscDynamicMaxDop function, the logic there seems to assume that numProcs is referring to the number of physical CPUs from the calculation that's being done, when in facts it counts "logical CPUs" - that is the number of processors that the OS reports ( equal to twice the number of cores in a HT environment):

    if ($numProcs -eq 1)
    {
        $dynamicMaxDop = [Math]::Round($numCores / 2, [System.MidpointRounding]::AwayFromZero)
    }

In this branch - dynamicMaxDop will always be 1 - as numProcs is actually the number of logical processors ( twice the number of cores in a hyper-threaded environment).
This branch would also only be entered if this script runs on a single-core, non-hyperthreaded machine (where numCores will also be 1).

Also, in the event of a machine with 2 sockets (NUMA nodes) with 2 cores each, according to the very latest version of the code in the repo, numCores will be 4 and, according to this branch:

else
    {
        $dynamicMaxDop = $numCores
    }

dynamicMaxDop would be set to 4, which is incorrect. In this case, it should actually be set to 2.

The Microsoft KB article on this topic lists the following logic:
https://support.microsoft.com/en-ie/help/2806535/recommendations-and-guidelines-for-the-max-degree-of-parallelism-confi

Suggestion
Loop through the NUMA nodes - pick the one with the lowest number of cores and use that as a the MAXDOP number if lower than 8, and 8 if equal to that or higher.
I don't know if there are any setups out there with a different number of cores per NUMA node, but the above should take care of that instance.

Locate Get-SqlDscDynamicMaxDop and trace how numProcs, numCores, and NUMA nodes are gathered for xSQLServerMaxDop. Compare the calculation with the linked Microsoft MAXDOP guidance, including single-node and multi-node scenarios. Done means the calculation uses the lowest logical-processor count per NUMA node, capped at 8, with coverage for the reported cases.