I dont think they necesswrily have the best intentions for interoperabillity.

Why wouldnt they do the same to Threema and Matrix/Elements/etc

The same stuff would likely apply to Threema, any chat app that publicly is known for e2ee and refuses to backdoor it will be fair game

There shouldnt be a difference but there is. Most iPhones require sideloading to get non-Apple App store apps.

The issue is for most people, if the government fucks around and gets Signal banned, Apple is their enforcer all the while harping about security and standards and other nonsense. Its horseshit because the lack of encrypted messengers like Signal makes people sitting ducks for surveillance and prosecution from a corrupt governement and Apple enforces their violent monopoly on deciding if the people using its products have safe access to quality, encrypted appz

I feel like the biggest issue is the lack of 3rd party app stores or the need to “sideload” as opposed to just fucking installing an application like any normal computer