Putting pressure on every alternative OS to do this would be silly. I'd be very surprised if (normal, Western democratic) governments do this. They'd need to go after every Android fork, pine phone, etc.
The much, much easier path is just to pressure the hardware manufacturers to stop allowing bootloader unlocking. There are only a few of them with significant market share, most wouldn't really care, and Google in particular would probably be ecstatic about it, since they couldn't be accused of being anti-competitive by following the law.
There will probably always be some way around this kind of thing; it'll just get harder is all. The point isn't to catch criminals or protect children; it's to enable mass surveillance of the population. As long as avoiding it is irritating enough for 95% of people, that's good enough.