[One (M8) General] skeletiko:
Finally got it!

Dear scotty1223, StuMcBill, Brds7t7, skulldreamz, miggsr, EddyOS, David Cogen from "The Unlockr" site, the always available Mr. Hofs and all the others that I may have forgotten to refer,..

THANK YOU ALL for your excellent support .. my HTC is finally stock (firmware and stock recovery) with my bootloader locked :D:D:D

Let me just make a quick summary for future reference for all other users that may also need to bring their HTC One m8 fully stock and that may find some of the (maybe noob) problems that I found..

Initial state: Unbranded HTC One m8 CID HTC__102 (s_off) with locked bootloader and with mikes1986 firmware ("Android Revolution HD 8.1 by mike1986")..

Main objective: return device to full stock firmware like if it was coming directly from store....

1. Used the excellent step by step tutorial from "The Unlockr" site in here..

2. Downloaded the Stock nandroid and stock recovery for my CID (in this specific case, I downloaded "1.12.401.17 - TWRP Thanks to MaximN97" and "stock recovery 1.12.401.17") from Mr. Hofs thread

3. After flashed the stock nandroid accordingly with the tutorial, I had trouble in flashing stock recovery... received error:

"writing 'recovery'

FAILED (remote: not allowed)

finished. (...)"

4. Mr. Hofs told me that was due to locked bootloader...

5. Unlocked the bootloader following Scotty1223's post

6. Flashed stock recovery flawlessly (following the above tutorial)..

7. Ignored every HTC system updates that I was already getting notified in the device (not sure if it would have any impact);

8. Tried to lock bootloader through the same post from Scotty1223, but no "# prompt" appeared when I was working with adb.. this was when I understood that this situation happened due to the fact that supersu had "disappeared" after flashed stock firmware (was unrooted)....

9. Downloaded supersu from Google Play... although, when I ran it.. I received the message that it "wasn't possible to install the binary (bla (...) bla (...)".. spent several days trying to understand how could I solve that, since, without supersu I couldn't lock the bootloader...

10. After lots of time spent and some posts...I finally got it... downloaded twrp's img (got it from here.. and placed it in fastboot directory and followed StuMcBill's tip

11. When I was rebooting system in TWRP it told me that system was unrooted and if I wanted to install supersu.. I've installed it... after system reboot.. I ran supersu.. it asked for the binary update (again the fuc**** binary)... therefore,.. I downloaded the SuperSU v2.02 update from here (CWM / TWRP / MobileODIN installable ZIP), placed it in a directory from phone's SD card..and once again ran TWRP without flashing it, thru StuMcBill's tip... selected Install option in TWRP, selected the directory where I've placed SuperSU v2.02 update and installed it....

12. After system reboot, Supersu was already working :highfive::highfive: ..locked the bootloader thru scotty1223's post already referred..

13. Reboot system,.. uninstalled supersu, thru its uninstall option.. and .. ended all this long journey :D :cool: :cool:

Hope that this could help anyone with the same problems.

Thank you and my apologies for the long post.

Best regards,

SkElEtIkO