Polar
Yeah I know there are quite a few discussions, about this topic in the EU. But at the moment there are a lot of voices on both sides so it is pretty undecided.
And the paragraph you postet is entirely to circumvent the appstore tax. It says nothing that apple has to allow any software or to run on their devices, or that they have to allow 3rd parties to install software they like.
The only thing it says is that apple would not be allowed to prevent app developers from implementing 3rd party payments circumventing the appstore payment system and therefore the apple-tax.
And even if this gets further that apple would have to allow a way to legally install 3rd party software on their devices this is just the EU. So this still would only work on devices sold inside the EU, apple will never open more then they have to by law. And I am pretty sure their will be no such laws in US or Asia.