Rooting the Galaxy Z Flip 3

There are plenty of posts out there explaining hot to root the Galaxy Z Flip 3. This is not one of them :-)

I tried the process described and failed miserably. When the phone booted again, or, rather, tried to boot again it complained about the software not matching and then rebooted. Upon the second reboot it entered a reduced recovery.

Here is why: none of the instruction mention that you have to factory reset your phone after flashing the patched boot partition and before the first boot.

Instruction do include unchecking "auto reboot" in Odin, but they fail to say that after flashing you need to turn off (vol down + power, hold for a while) and then boot into recovery (vol up + power, be quick to switch your fingers, the phone will turn itself on and boot the system if you are slow).

With this addition, which I found in a single post on XDA developers (thanks you!) it worked.

As the posts suggest different methods, here is the minimal method that I found working: you only have to patch the boot partition using Magisk.

If you are not sure whether your downloaded firmware image matches the one installed on your phone, just flash the complete AP package before patching the boot partition, to be on the safe side.