Was done on 8.1.7.50, just upgraded to 8.1.7.109 and doing the whole process again:
1. on first boot, alternatively tapping top right and left corner and enter EasterEggActivity
2. enter diagnostic -> android development settings -> unlock with password NOOK-BNRV1300
3. turn on "OEM unlocking" and "USB debugging"
3.1 adb devices (pop up in device to allow USB debugging access; make sure devices is authorized)
4. adb push boot.img /sdcard/ (extracted from update.zip for matching version,
8.1.7.109)
5. adb install magisk.apk (
using v24 from official github release of magisk this time)
6. adb shell am start com.topjohnwu.magisk/.ui.MainActivity
6.1 patching boot.img in launched magisk
7. adb pull /path/to/patched_boot.img (should be /sdcard/Download/magisk_patched-24000_XXXXX.img)
8. adb reboot bootloader
8.1 fastboot devices (to make sure the device is in fastboot/bootloader mode)
9. fastboot flash boot patched_boot.img
10. fastboot reboot
That's it.
Since this version of magisk is taken from the official github release, the security risk should be smaller. I think the latest (or newer) version of magisk introduced some incompatibility and cause it not working for GL4+. The version by erkins007 is a debug version between v23 and v24, so I use v24 this time and it worked.