[One (M8) Android Development] nightcervant:
Hello everyone , I am allowed to change the FW Marshmallow so not using the WIPE of internal memory and additionally install the latest TWRP recovery.

Necessary:

1. HTC ONE M8 UL S-OFF

2. FW MOD MM: DOWNLOAD

3. ADB/Fastboot

Let's Start:

1. Download FW, copy to ADB Folder and rename to:

firmware.zip

2. Reboot to Bootloader your M8 and let's get into RUU mode, Open terminal to ADB folder and give the following command:

fastboot oem rebootRUU

3. Now flash Firmware mod:

fastboot flash zip firmware.zip

4. Now check the console output. It should approximately look like this:

iMac-di-Francesco:ANDROID francesco$ ./fastboot flash zip firmware.zip

target reported max download size of 1826418688 bytes

sending 'zip' (28699 KB)...

OKAY [ 2.105s]

writing 'zip'...

(bootloader) zip header checking...

(bootloader) zip info parsing...

(bootloader) checking model ID...

(bootloader) checking custom ID...

(bootloader) total_image_number=9

(bootloader) start image[adsp] unzipping & flushing...

(bootloader) [RUU]UZ,adsp,0

(bootloader) [RUU]UZ,adsp,11

(bootloader) [RUU]UZ,adsp,22

(bootloader) [RUU]UZ,adsp,32

(bootloader) [RUU]UZ,adsp,43

(bootloader) [RUU]UZ,adsp,54

(bootloader) [RUU]UZ,adsp,65

(bootloader) [RUU]UZ,adsp,76

(bootloader) [RUU]UZ,adsp,87

(bootloader) [RUU]UZ,adsp,98

(bootloader) [RUU]UZ,adsp,100

(bootloader) [RUU]WP,adsp,0

(bootloader) [RUU]WP,adsp,100

(bootloader) ...... Successful

(bootloader) current_image_number=0

(bootloader) start image[rpm] unzipping & flushing...

(bootloader) [RUU]UZ,rpm,0

(bootloader) [RUU]UZ,rpm,100

(bootloader) [RUU]WP,rpm,0

(bootloader) [RUU]WP,rpm,100

(bootloader) ...... Successful

(bootloader) current_image_number=1

(bootloader) start image[sbl1] unzipping & flushing...

(bootloader) [RUU]UZ,sbl1,0

(bootloader) [RUU]UZ,sbl1,100

(bootloader) signature checking...

(bootloader) verified fail

(bootloader) ..... Bypassed

(bootloader) current_image_number=2

(bootloader) start image[sbl1] unzipping & flushing...

(bootloader) [RUU]UZ,sbl1,0

(bootloader) [RUU]UZ,sbl1,100

(bootloader) signature checking...

(bootloader) [RUU]WP,sbl1,0

(bootloader) [RUU]WP,sbl1,100

(bootloader) ...... Successful

(bootloader) current_image_number=3

(bootloader) start image[sbl1] unzipping & flushing...

(bootloader) [RUU]UZ,sbl1,0

(bootloader) [RUU]UZ,sbl1,100

(bootloader) signature checking...

(bootloader) verified fail

(bootloader) ..... Bypassed

(bootloader) current_image_number=4

(bootloader) start image[sensor_hub] unzipping & flushing...

(bootloader) [RUU]UZ,sensor_hub,0

(bootloader) [RUU]UZ,sensor_hub,100

(bootloader) [RUU]WP,sensor_hub,0

(bootloader) [RUU]WP,sensor_hub,4

(bootloader) [RUU]WP,sensor_hub,8

(bootloader) [RUU]WP,sensor_hub,12

(bootloader) [RUU]WP,sensor_hub,16

(bootloader) [RUU]WP,sensor_hub,20

(bootloader) [RUU]WP,sensor_hub,24

(bootloader) [RUU]WP,sensor_hub,28

(bootloader) [RUU]WP,sensor_hub,32

(bootloader) [RUU]WP,sensor_hub,36

(bootloader) [RUU]WP,sensor_hub,40

(bootloader) [RUU]WP,sensor_hub,44

(bootloader) [RUU]WP,sensor_hub,48

(bootloader) [RUU]WP,sensor_hub,52

(bootloader) [RUU]WP,sensor_hub,56

(bootloader) [RUU]WP,sensor_hub,60

(bootloader) [RUU]WP,sensor_hub,64

(bootloader) [RUU]WP,sensor_hub,68

(bootloader) [RUU]WP,sensor_hub,72

(bootloader) [RUU]WP,sensor_hub,76

(bootloader) [RUU]WP,sensor_hub,80

(bootloader) [RUU]WP,sensor_hub,84

(bootloader) [RUU]WP,sensor_hub,88

(bootloader) [RUU]WP,sensor_hub,92

(bootloader) [RUU]WP,sensor_hub,96

(bootloader) [RUU]WP,sensor_hub,100

(bootloader) ...... Successful

(bootloader) current_image_number=5

(bootloader) start image[tz] unzipping & flushing...

(bootloader) ...... Successful

(bootloader) current_image_number=6

(bootloader) start image[wcnss] unzipping & flushing...

(bootloader) ...... Successful

(bootloader) current_image_number=7

(bootloader) start image[radio] unzipping & flushing...

(bootloader) trying to rename MBA

(bootloader) ...... Successful

(bootloader) current_image_number=8

OKAY [ 56.209s]

finished. total time: 58.314s

Important: the flash process halts at around 75% to 90% on phone screen! This is normal and a safety precaution! The last few percent is the reboot, which is NOT happening automatically, so you get a chance to check the console output to make sure it is safe to reboot! The bar will only fill up to 100% once you type:

fastboot reboot