Micro-LEDs boost random number generation

My first question would be whether it's possible to influence the output via triggering power fluctuations on the motherboard - e.g. by running expensive code to cause the CPU/GPU to scale up.

Probably not. It's hard to guess, but they probably get a Poison Distribution https://en.wikipedia.org/wiki/Poisson_distribution in the detector, they may read only a few of the lower bits of the data, and then mix them in the entropy pool, with other sources. So the end result is quite unpredictable.

It's somehow similar to a random generator where you have 5 dices, roll them and then add to the entropy pool only if the total was even or odd. Changing the power is like forcing the system to use only 4 dices. It changes the probabilities a little, but not in a very controlable way, and with a good mixing in the entropy pool it's almost irrelevant.