Rooted devices & custom roms, depending on your jurisdiction are illegal or might as well be, they also require a intermediate tech knowledge, and in the case of custom ROMs, google just gutted the development cycle for aosp. Adb is by definition for developers, and I don’t know what you mean by non-certified android devices.

All in all, it seems like only tech enthusiasts living in places that are pro right to own & repair will ever take advantage of this, which means in practice, there are only two platforms for the average consumer and both are attempting to stop you from circumventing their walled gardens.