Installation instructions:

For sideload:

• Download recovery.img in download link
• Reboot phone to bootloader
• Open any terminal like cmd etc, enter "fastboot flash recovery recovery.img"
• Reboot phone to recovery and enter sideload mode
• Enter "adb sideload xxx" (xxx means the filename of rom zip you downloaded)
• Do factory reset in recovery (Mandatory for first time flash)
• Reboot

You can also use rom installer to flash the way you did before.

For root:

• Download Magisk apk
• Rename it to *.zip
• Reboot to recovery and enter sideload mode
• Enter "adb sideload xxx.zip" (xxx means magisk file name)

You can also patch boot.img and flash via fastboot.