MODELSIM Demultiplexer simulation fails. Hidden Altera internal modules(?)

I believe I have found an answer for all those who might search for it: It is simply not provided for by Altera.

Chapter 18 of the UG-01085 Embedded Peripherals IP User Guide (2016) says the following:

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Hardware Simulation Considerations

The multiplexer and demultiplexer components do not provide a simulation testbench for simulating a stand-alone instance of the component. However, you can use the standard SOPC Builder simulation flow

to simulate the component design files inside an SOPC Builder system.

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It is thus not possible to simulate an isolated extraction of either the multiplexer or demultiplexer components.