If software is sold that requires access to a server, for example, and the company stops supporting it, they should be required to release the tech specs that would allow anyone to run their own server.

Few games creators do exactly that. So this is not just some wishful thinking, it really works in real world. As benefit, such companies gain respect among customers, wich is hard to gain, but easy to loose.

While it would be nice if companies had to continue to maintain their products, I don't think that would be legally enforceable and it would be simpler all around to just release their monopolies and let people do what they like.

Manufacturers easily enforced to many unreasonable and even just insane regulations without any problem. Just recall that multilayer hoax with freon refrigerants - first, fridge manufacturers was forced to switch to freon due to "explosivity" of propane/butane and ammonia, then forced back to propane/butane due to "ozon holes"