I'd settle for open API's at this point. And honestly to me seems like a fairly natural way to do "anti-trust" without actually breaking up companies in a potentially destructive way. If other people can make slack clients, or pull "popular times" information from google places, or aggregate instagram live / facebook live videos, that would go a long way towards an open (and competitive!) ecosystem.
Ideally, we'd all be mostly following and investing in extending existing standards for chat/etc. e.g. RFC 1459 doesn't have everything that slack/Teams/etc needs but there's no good reason that Microsoft can't throw some money at IETF to help them grow the standard to what we need for modern business chat.
Separately, I could see anti-trust legislation requiring internal API's to be made accessible to competitors and billed at the same rates as internal API requests from one business segment to another. E.g. Google Maps would pay Google Places for the info that it serves up, but Yahoo Maps could re-skin that info or combine it with other sources as well if they pay the same rates that Google Maps does.