Most likely, it would look like Asahi Linux, which has managed to reverse engineer and re-implement many parts of the Mac environment relatively quickly in Linux. If it works like the Mac does, we may see a project to make a custom ROM for iPhone (probably a fork of either a Linux phone project or of AOSP) soon after the responsive update, and within about a year of that, we might see it be fairly usable.
Some nits: Apple could access many classes of data stored on iCloud by default (including any photos), even now, but you can make almost every class end to end encrypted now if you explicitly chose to. Previously, and by default now, it’s Apple policy and internal controls over the keys your data is encrypted with that protect that data, not the encryption itself (though you can opt in to the encryption itself protecting you from Apple). From what I understand, Apple is only known to actually scan iCloud mailboxes regularly, with the on-device scanning having never been implemented. Outside of nits, considering the delay between the proposed scanning and offering of a wider E2EE program for iCloud, I doubt the two are actually related myself.
A game where using the in-build chat is a bannable offense.
That’s true, but macs also do have more security controls, configured more sensibly by default. BitLocker, the system’s full disc encryption feature for example, is still considered a premium product reserved for more expensive editions, whereas macs, android, and iOS have had it standard and default enabled (the latter two with no option to disabled it) in current versions for years. Windows still does not require (or last I checked even offer) things like application sandboxing or runtime hardening by default (this may well have changed in the past couple of years, but I’ve heard nothing of it). While the Universal Windows Platform does have a functional permissions system, that whole platform is (as I understand it) limited to the Microsoft store (which as I understand is ignored by vendors), and the last time I looked at it, it was a mess. There are other such things. Which isn’t to say macs can’t get malware, they can, and they’ll get more malware as time goes on. There are other measures set up on Windows but not macOS, but they don’t appear to be as effective to me, and they seem to be mainly focused on reacting to specific incidents. Security-wise, the two really are not the same.