> Why are there not yet a plethora of phones on the market that allow anyone to install their OS of choice?

There are technical reasons, but as ever the real underlying causes are incentives. Companies realized that the OS is a profit center, something they can use to influence user behavior to their benefit. Before the goal was to be a hardware company and offer the best hardware possible for cost. Now the goal is to own as large a slice of your life as possible. It's more of a social shift than a technological one. So why would a company, in this new environment, invest resources in making their hardware compatible with competing software environments? They'd be undercutting themselves.

That's not to say that attempts to build interoperability don't exist, just that they happen due to what are essentially activist efforts, the human factor, acting in spite of and against market forces. That doesn't tend to win out, except (rarely) in the political realm.

i.e. if you want interoperable mobile hardware you need a law, the market's not going to save you one this one.

Most ARM devices don't have UEFI or a standardized hardware abstraction layer as x86/x64 does, a prerequisite for having a choice of OSes.

I generally agree, but as a caveat sometimes it's cheaper, more robust and more efficient to build an integrated system without having to worry about interoperability. BYD's electric vehicle chasis for example, seems to greatly cut manufacturing costs, even if it makes swap-in repairs harder down the road.

But, I'd guess this accounts for a relatively small fraction of corporate decision on lock-in strategies for rent extraction - advanced users should be able to treat their cell phones OS like laptops, with the same basic concepts, eg just lock down the firmware for the radio output, to keep the carriers happy, and open everything else, maybe with a warranty void if you swap out your OS. Laws are needed for that, certainly.

> So why would a company, in this new environment, invest resources in making their hardware compatible with competing software environments?

Because that's what customers want to buy. People are paying premium iPhone prices for hardware with mediocre specs and then the hardware sells out when someone like Purism or Fairphone actually makes an open one. How many sales would you get if you did the same thing on a phone that was actually price/performance competitive with the closed ones?

Meanwhile all of that "profit center" talk is MBA hopium. Nobody is actually using the Xiaomi App Store, least of all the people who would put a different OS on their phone.

The real problem here is Google. Hardware attestation needs to be an antitrust violation the same as Microsoft intentionally breaking software when you tried to run it on a competing version of DOS and for exactly the same reason.