...we would not have the modular desktop PC and we would not have Linux.
There’s probably no way to support that counter-factual. We could easily have ended up with some other open-architecture personal computer and open source operating system.
Thats just one simple example I can think of. Intel, as well, was never monopolized as a chip manufacturer. They could sell chips freely to IBM competitors.
Also, the reverse engineering of the IBM platform is what made Compaq computer successful in the mid 80s.
I don't think even a quick examination of the histories involved here would yield any other result than open hardware and software was always going to be a big component of desktop computing.
These things ebb and flow anyway, historically what you usually see is that for at least a decade (sometimes more, a lot more, and sometimes dramatically less) what ends up happening is vertically integrated solutions are favored as they bring the most harmony to the average customer of said platform ('it just works!' was as slogan of many firms, not just Apple). Then as complexities can be either mitigated or eliminated these things tend to open themselves up.
I believe Mobile devices are going through this phase. I think in another decade or two you will have a situation where you start seeing really useable open alternatives to the major platforms even though right now it does not seem intuitive or obvious how that will work
There’s probably no way to support that counter-factual. We could easily have ended up with some other open-architecture personal computer and open source operating system.