Apple's policies have always been extremely closed regarding other company's software. The whole logic of the Apple system is to tie the customer to proprietary software and hardware, e this also applies to cloud gaming systems.
However, it seems that the state of affairs may soon change. Business Insider reports that in recent weeks the Xbox team responsible for the development of the Game Pass and xCloud held some meetings to be able to introduce their software into the apple ecosystem without breaking the rules.
The obstacle to overcome is not the simplest. Apple recently showed a small opening, allowing in theory the cloud gaming services of Google (Stadia) and Microsoft (precisely xCloud) to land on their mobile devices. However, this can only happen on condition that the games are available on the App Store, and that users can review them. Apparently acceptable condition, but actually very expensive, given that Apple takes 30% of every transaction that takes place on its store.
Microsoft's solution to this problem would be to create software that works via a browser, including Safari. This would allow you to land on iOS without being forced to go to the App Store.
Simple operation then, and from the meetings already mentioned it would seem a lot of optimism, but it should be remembered that someone has already tried to do something similar, and it did not end well at all. When Epic Games has tried to free Fortnite's internal transactions from Apple's "tax", the company responded by removing the game from its devices. The matter will only be resolved in front of a judge, but in the meantime Fortnite has lost many players due to the Ban.
Microsoft seems convinced, however, and perhaps this operation will be able to breach the isolation of Apple devices.