If you don't accept push notifications, sure, you wouldn't technically be using APNS - the tokens change every time you give access for notifications. Last I checked, there's a connection to APNS running on every device or something... so blocking it would be interesting.

You'll be SOL on iOS anyway, ultimately - you're def not building it yourself with Xcode without an Apple account. Jailbreaking may be a fit here, but in defense of Signal, jailbreaking was kinda dead for a few years and only recently became usable again. Altstore[1] is... interesting, but I don't have enough experience with it to comment further.

I get what you're after, but Signal's not about to ignore the massive iOS userbase, and these are defining parts of the iOS ecosystem currently. You either play by those rules or you probably don't grow.

[1] https://altstore.io