It is very important to follow this procedure exactly and dont bypass any step when you root Samsung device :
A10-20-30-50-70-Note 10 -Note10+ and any device comes with base android version 9.0 …
1- Make Root kernel .
2- Unlock bootloader
3- Make Sure RMM or KG is stopped .
How to stop RMM or KG in most devices .
Flash full stock rom , once device bootup choose language and connect to wifi then continue with device setup until you reach the desktop then enable Dev mode and wait til OEM show up , enable it and you are done
4- Reboot to recovery
5- Do factory Reset
6- Reboot to download mode
7- Press & Hold Volume up and start flashing the root kernel , release the Volume up button when the first logo appears
8- Now your device is rooted.
9- Next time you want to get root access just turn off your device press volume up and start device .