Internet search reveals a couple of ways of doing this:
This reddit post suggests a couple of methods, which are simple
In contrast, this XDA mentions that even flashing boot.img is not enough and you need to clean flash system as well - in other words complete ROM
Do I run a risk if I choose the first method and flash the last version of traditional root?
Anything else I need to bear in mind ?
Edit: Any other method ?
I had this very issue some time ago. In my case, this Reddit post helped.
Basically, to migrate to the traditional system root, you need to have the TWRP recovery installed, the latest SuperSU flashable ZIP, your phone to be already systemlessly rooted and SuperSU by Chainfire to be your root manager app.
Next, boot to Android, open SuperSU and navigate to the Settings tab. Find the Full Unroot button and tap it. When SuperSU asks if you're sure to unroot, accept. When it asks whether to restore the old boot.img, deny.
When the phone reboots, input the appropriate keys and boot into TWRP. Once there, make sure that the /data partition be mounted. Then, under the Advanced menu, start TWRP's Terminal and issue the following commands:
cd /data
echo SYSTEMLESS=false > .supersu
. Alternatively, you can use
echo SYSTEMLESS=false > /data/.supersu
to achieve the same result. This creates the file .supersu inside /data.
Finally, flash the SuperSU ZIP to force SuperSU to use the standard, old root procedure.
This file is checked (e.g. sourced) by the SuperSU ZIP. If it finds the entry SYSTEMLESS and it has value false, the installer will perform a system install. If the value is true, the installation will be systemless.
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