BackDoorLock will not protect you from an OTA update.
Use the blocker directory name given in the spoiler of Step #7.
I would really like to write an easier to understand set of directions.
All I can say for the current version is that it is a lot better than it was six weeks ago.
Note:
At least until we get a chance to take a close look at the situation,
avoid 5.8.2 on any of the devices.
The new KUAL booklet may not run under 5.8.2 and our maintainer of that is on a (short) holiday.
I will be expanding Step #7 to give direct download links for both 5.8.1 and 5.8.2 someday, RSN.
Alex has recently given approval for direct links on this forum.