While it’s true that not all dark matter has to be exactly the same thing, it’s also true that no large portion of it can be ordinary baryonic matter at low tem

While it’s true that not all dark matter has to be exactly the same thing, it’s also true that no large portion of it can be ordinary baryonic matter at low temperatures. What we know about dark matter is that it is weakly interacting, which means that it just doesn’t interact with ordinary matter and ordinary energy. This automatically rules out building a machine made of ordinary matter that creates or manipulates dark matter on any large scale. We might conceivably build a giant machine that _detects_ a particle or two of dark matter every year, but so far all our attempts have failed. Thus dark matter cannot just be a waste product of some advanced civilization, and even if it were you cannot just magic up a way to avoid creating waste heat.