[One (M8) Q&A, Help & Troubleshooting] nkk71:
good firmware thread: http://xdaforums.com/htc-one-m8/development/progress-fuu-m8-t2813792

provided you have a M8_UL (ie GSM single-sim HTC One M8), then you could update to: 4.16.401.10

this is what the flash should look like:

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot devices[/COLOR][/B]
SHxxxxxxxxxx fastboot [I][COLOR="Purple"]<- we are in bootloader[/COLOR][/I]

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot getvar all[/COLOR][/B]
(bootloader) version: 0.5
(bootloader) version-bootloader: 3.19.0.0000
(bootloader) version-baseband: 1.25.214500021.06G
(bootloader) version-cpld: None
(bootloader) version-microp: None
[B][COLOR="Blue"](bootloader) version-main: 3.28.401.9[/COLOR][/B]
(bootloader) version-misc: PVT SHIP S-OFF
(bootloader) imei2: Not Support
(bootloader) meid: 00000000000000
(bootloader) product: m8_ul
(bootloader) platform: hTCBmsm8974
(bootloader) modelid: 0P6B10000
(bootloader) cidnum: 11111111
(bootloader) battery-status: good
(bootloader) battery-voltage: 0mV
(bootloader) partition-layout: Generic
(bootloader) security: off
(bootloader) build-mode: SHIP
(bootloader) boot-mode: FASTBOOT
(bootloader) commitno-bootloader: 3aa067db
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0
all: Done!
finished. total time: 0.157s

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot reboot-bootloader[/COLOR][/B]
rebooting into bootloader...
OKAY [ 0.017s]
finished. total time: 0.019s

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot oem rebootRUU[/COLOR][/B]
...
(bootloader) Start Verify: 0
OKAY [ 0.021s]
finished. total time: 0.022s

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot flash zip M8_4.16.401.10_WWE_TWRP2840_NoWipe_rename_to_ROM.zip[/COLOR][/B]
target reported max download size of 1826418688 bytes
sending 'zip' (42631 KB)...
OKAY [ 2.958s]
writing 'zip'...
(bootloader) zip header checking...
(bootloader) zip info parsing...
(bootloader) checking model ID...
(bootloader) checking custom ID...
(bootloader) start image[hboot] unzipping for pre-update check...
(bootloader) total_image_number=8

(bootloader) start image[hboot] flushing...
(bootloader) [RUU]WP,hboot,0
(bootloader) [RUU]WP,hboot,99
(bootloader) [RUU]WP,hboot,100
(bootloader) ...... Successful
(bootloader) current_image_number=0

(bootloader) current_image_number=1

(bootloader) current_image_number=2

(bootloader) current_image_number=3

(bootloader) current_image_number=4

(bootloader) current_image_number=5

(bootloader) current_image_number=6

(bootloader) current_image_number=7

FAILED (remote: 90 hboot pre-update! please flush image again immediately)
finished. total time: 4.227s

^^ note the hboot preupdate error, so you need to flash a second time to continue the update:

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot flash zip M8_4.16.401.10_WWE_TWRP2840_NoWipe_rename_to_ROM.zip[/COLOR][/B]
target reported max download size of 1826418688 bytes
sending 'zip' (42631 KB)...
OKAY [ 2.967s]
writing 'zip'...
(bootloader) zip header checking...
(bootloader) zip info parsing...
(bootloader) checking model ID...
(bootloader) checking custom ID...
(bootloader) total_image_number=17

(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,88
(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[pg2fs_spcustom] unzipping & flushing...
(bootloader) [RUU]UZ,pg2fs_spcustom,0
(bootloader) [RUU]UZ,pg2fs_spcustom,23
(bootloader) [RUU]UZ,pg2fs_spcustom,45
(bootloader) [RUU]UZ,pg2fs_spcustom,67
(bootloader) [RUU]UZ,pg2fs_spcustom,88
(bootloader) [RUU]UZ,pg2fs_spcustom,100
(bootloader) ...... Successful
(bootloader) current_image_number=1

(bootloader) start image[recovery] unzipping & flushing...
(bootloader) [RUU]UZ,recovery,0
(bootloader) [RUU]UZ,recovery,7
(bootloader) [RUU]UZ,recovery,13
(bootloader) [RUU]UZ,recovery,19
(bootloader) [RUU]UZ,recovery,28
(bootloader) [RUU]UZ,recovery,33
(bootloader) [RUU]UZ,recovery,38
(bootloader) [RUU]UZ,recovery,71
(bootloader) [RUU]UZ,recovery,76
(bootloader) [RUU]UZ,recovery,83
(bootloader) [RUU]UZ,recovery,89
(bootloader) [RUU]UZ,recovery,95
(bootloader) [RUU]UZ,recovery,100
(bootloader) [RUU]WP,recovery,0
(bootloader) [RUU]WP,recovery,100
(bootloader) ...... Successful
(bootloader) current_image_number=2

(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=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[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=5

(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=6

(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=7

(bootloader) start image[sdi] unzipping & flushing...
(bootloader) [RUU]UZ,sdi,0
(bootloader) [RUU]UZ,sdi,100
(bootloader) [RUU]WP,sdi,0
(bootloader) [RUU]WP,sdi,100
(bootloader) ...... Successful
(bootloader) current_image_number=8

(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=9

(bootloader) start image[tp] unzipping & flushing...
(bootloader) ..... Bypassed
(bootloader) current_image_number=10

(bootloader) start image[tp] unzipping & flushing...
(bootloader) ..... Bypassed
(bootloader) current_image_number=11

(bootloader) start image[tz] unzipping & flushing...
(bootloader) ...... Successful
(bootloader) current_image_number=12

(bootloader) start image[wcnss] unzipping & flushing...
(bootloader) ...... Successful
(bootloader) current_image_number=13

(bootloader) start image[radio] unzipping & flushing...
(bootloader) trying to rename MBA
(bootloader) ...... Successful
(bootloader) current_image_number=14

(bootloader) start image[rcdata] unzipping & flushing...
(bootloader) ...... Successful
(bootloader) current_image_number=15

(bootloader) start image[emmc_fw16] unzipping & flushing...
(bootloader) ...... Successful
(bootloader) current_image_number=16

OKAY [ 65.276s]
finished. total time: 68.250s

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot reboot-bootloader[/COLOR][/B]
rebooting into bootloader...
OKAY [ 0.017s]
finished. total time: 0.019s

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot getvar all[/COLOR][/B]
(bootloader) version: 0.5
(bootloader) version-bootloader: 3.19.0.0000
(bootloader) version-baseband: 1.25.214500021.06G
(bootloader) version-cpld: None
(bootloader) version-microp: None
[B][COLOR="Blue"](bootloader) version-main: 4.16.401.10[/COLOR][/B]
(bootloader) version-misc: PVT SHIP S-OFF
(bootloader) imei2: Not Support
(bootloader) meid: 00000000000000
(bootloader) product: m8_ul
(bootloader) platform: hTCBmsm8974
(bootloader) modelid: 0P6B10000
(bootloader) cidnum: 11111111
(bootloader) battery-status: good
(bootloader) battery-voltage: 0mV
(bootloader) partition-layout: Generic
(bootloader) security: off
(bootloader) build-mode: SHIP
(bootloader) boot-mode: FASTBOOT
(bootloader) commitno-bootloader: 3aa067db
(bootloader) hbootpreupdate: 11
(bootloader) gencheckpt: 0
all: Done!
finished. total time: 0.157s

C:\ADB5_1.0.32>[B][COLOR="Blue"]fastboot reboot[/COLOR][/B]
rebooting...

finished. total time: 0.017s