I am not sure about this - does install any software also mean system software or is it only meant to allow installation from sources other than their own app s

I am not sure about this - does install any software also mean system software or is it only meant to allow installation from sources other than their own app store? To allow system software installations, Apple (and other mobile device manufacturers) will have to allow unlocking the bootloader. (But that alone is limited as without the hardware information of the individual parts, developing an alternate OS for such devices is painful work as you have to essentially reverse engineer everything to create the device drivers - as evident with the snail's pace that Asahi Linux are progressing at to port Linux to Apple M1 and M2 ARM processors. Unless ofcourse, the DMA also forces them to publish the hardware literature so that other system developers can use it, which would be a real game changer ... ).