For a start, and it might even be enough, you strictly enforce anti-trust laws which are already on the books that prevent sufficiently large firms from acquiring their competitors and doing exclusivity deals. These laws have largely been ignored for decades and I don't know what to call that other than blatant corruption of our government, but it's slowly starting to change, in a bipartisan way.

Microsoft escaped the worst of what the government wanted to do to them for their anti-trust violations. It may not go so well for Google as they hold the distinction of being the only company in US history to have been tried and found guilty in three separate cases of possessing three illegal monopolies all at the same time. Two example measures under discussion in the court at the moment are forbidding any renewal of their browser default deal with Apple, and forcing them to sell off Chrome. We will see soon enough what comes next.