Stefan-Boltzmann is about absolute, not relative temperature.

When one does the math on the operating temperatures of regular computing equipment that we use on Earth, how much heat it generates per watt, and how fast it would need to sink that heat to allow for continuous operation, one gets surface areas that are not impossible, but are pretty on the high end of anything we've ever built in space.

And then you have to deflect the incoming light from the Sun which will be adding to your temperature (numbers published by private space companies regarding the tolerances of payloads those companies are willing to carry note that those payloads have to be tolerant of temperatures exceeding 100° C, from solar radiation alone). That is doable, you could sunshield the sensitive equipment and possibly decrease some of your thermal input load by putting your craft out near L2 which hangs out in the penumbra of Earth. Still a daunting technical challenge when the alternative is just build it on the planet with the technology and methods we already have.