As I mentioned I'm not following this case really at all, but some initial thoughts from your comment are that while Apple doesn't have a monopoly on smart phones, they do have a monopoly on what software users can run on the phones and tablets they make (so if you define platform as "smartphones" then no monopoly, if platform is "iOS" then yes monopoly).

On the Android side of things, Google doesn't have near the same level of control, so that is false equivalence. One can easily side load apps, and people do all the time (Fortnite for example, couldn't happen on iOS but did on Android). There's also competing app stores (F-Droid, Amazon App store), so a very different situation. You can also run any OS you want on your device if Google's Android flavor isn't to your liking. Google also doesn't make/sell most of the hardware.

Microsoft got in trouble for simply making it very easy for people to use IE instead of Netscape and Word instead of WordPerfect. Imagine if they had gone a step further and mandated that only apps that pass a Microsoft review process could even be installed at all?

Microsoft got into trouble because Windows had a very dominant market position (80%+)

iOS does not because there are more Android devices than iOS devices.

Regarding your first part about apple having a monopoly on what runs on an iPhone: so does Samsung on fridges/washing machines/ovens, or almost any other embedded system for that matter. My router-maker also does not allow me to put different software on my router, and I can’t run software that hasn’t been allowed explicitly by Microsoft/Sony on an Xbox/Playstation.

This is ‘whataboutism’ but why is it only an issue for Apple devices but A-OK and ‘normal’ for every other example?

AFAIK that's not how it works. For example go look up Microsoft's monopoly. The commonly held believe is Microsoft was declared to have a monopoly on personal computer OSes but that is false. Microsoft was found to have a monopoly on OSes for Intel based machines. So by that same logic Apple has a monopoly on OSes for A series (A10, A11, A12) based smartphones.

https://en.wikipedia.org/wiki/United_States_v._Microsoft_Cor....

Can a company have a monopoly over its own products? That doesn't make sense.

iOS apps aren't Apple's products.

I was talking about the processor series.

A-series chips are just (very good) ARMs. I don’t buy that equivalence at all.