> that the vast majority of phones these days have their bootloaders locked.

I don't know if that is actually still true. Back in the day nearly every phone in the US was bootloader and carrier locked. Now basically every phone is carrier unlocked and anything besides Samsung can have the bootloader unlocked very easily. I guess Samsung phones are the most common but there are certainly many other options that are more open.

This seemed unlikely since S10 is maybe the most mainstream flagship phone but it appears that Samsung does indeed make it painful to take control of your device: https://topjohnwu.github.io/Magisk/install.html#samsung-syst...

Many manufactures make it easy to unlock and root your device (shout-out oneplus), but many others do try to make you brick it if you try doing anything out of the ordinary. Like the HMD rebrands Nokia, Sharp, etc.

Oneplus requires you to wipe your phone to root it. Add to this that there is no way to backup the phone without rooting it.

You can get the same backups you would have if you never rooted it to start with. I agree in some cases that's not enough but it's not no backups of any sort. Mostly just more hassle to restore.

Of course, everyone requires a wipe. That's to protect normies' data when they inevitably get their stuff stolen on a trip to Paris. Easy to live with, just root it first thing after unboxing.

Samsungs are locked there?

Here in europe, you go to developer mode, check the OEM unlock button, reboot and hold some weird button combination while booting, phone asks you again if you want to unlock the bootloader, does a factory reset for security reasons, another reboot, and it's unlocked.