Prerequisites:
Warning:
The actions below might damage your device, so good to use Google Nexus or Pixel series that they can flash with system image to recover easily !!
Tool 1:
Download and install Android SDK from https://developer.android.com/studio in order to have adb command
Tool 2:
Download Magisk from https://github.com/topjohnwu/Magisk , e.g.: Magisk-v20.4.zip
Tool 3:
Download TWRP for your device from https://twrp.me/Devices/
a. Look for TWRP for Pixel 3 XL from https://dl.twrp.me/crosshatch/
b. Download twrp-3.3.1–3-crosshatch.img
Step 1:
Enable developer option on device, refer to https://developer.android.com/studio/debug/dev-options#enable
Steps:
Step 1:
Connect your device to PC / Mac machines via USB
Step 2:
Copy Magisk file into device by running command “adb push Magisk-v20.4.zip /sdcard/”
Step 2:
Run command “adb reboot bootloader” then your device will be on bootloader mode
Step 3:
Run command “fastboot boot twrp-3.3.1–3-crosshatch.img ”, assume twrp-3.3.1–3-crosshatch.img is in same directory
Step 4:
Tap Install and install Magisk
Step 5:
Reboot
Step 6:
Run command “adb shell” then “su” to see whether it’s successful ?!
Good luck !!