SIM/operator locks have been already rare (in Europe) for a while, and that's great!

But there are Android phones that come with bootloader/OS lock, which often means old device is stuck with some ancient OS version (and some bundled bloatware), instead of being able to be reflashed to a recent LineageOS.

Even LineageOS can only help so far. I've got a Galaxy S7 Edge, bought it dec. 2016. It's not even supported by Lineage OS any more.

You should switch to the official OS then - it just got an update. As it also did 3, 6 and 12 months ago.

What are you talking about? The last update for the "official" OS was for Android 8.0. That was two years ago.

Mine got OS update just this week. Not sure what the Android version is though, it's now my girlfriend's phone. It did the OS reinstall screen.

Are you talking about quarterly security patches...?

Xiaomi's phones are locked like this, requiring a mi account to unlock the device to allow flashing thé device...

The new phone lock du jour is the manufacturer's anti theft mechanism.

I recently got two iphones from their owners, pulled out of the drawer to monetize them on classifieds. Both locked and unresettable without the previous owners help (one could be unlocked because I got her account password over the phone, huge nogo but she trusts me to not screw with her account). The other not, account was lost.

Apple also now tags and ties both battery and camera to the logicboard. Shame.

This one is a pretty obvious trade off, does anyone know of good data on the impact of Apples policy on iphone theft rates and/or sales rate of stolen phones?

You can't find a Macbook in any second hand store around Prague. It used to be full of them.