iPhone 7 with dead NAND netbooting unmodified Ubuntu 20.04 via USB ethernet
It would be a potentially smart move by Apple to allow installing other OSs in iOS hardware. The market share grab part of this segment is mostly gone so they probably wouldn't lose much and it would help with their arguments about the App Store and other iOS restrictions. They could say that in iOS those are the rules but if you want to do something else with the device you own you can install something else. It might even win them some customers. They would win my business if I could install an open-source OS under my control on a phone like I do on my laptop. LineageOS is not even close unfortunately because of poor hardware support.