[Fire HD 8 and HD 10 Original Android Development] DragonFire1024:
here is the output from the test I ran on my working tablet last night that stops at userdata:

dragon@dragonfire:~/amonet-suez2/amonet$ sudo ./step-1.sh

* daemon not running. starting it now on port 5037 *
* daemon started successfully *
Testing root access...

Trying to use mtk-su to get temp root...
No mtk-su found, you can get it here: https://xdaforums.com/hd8-hd10/orig-development/experimental-software-root-hd-8-hd-10-t3904595
dragon@dragonfire:~/amonet-suez2/amonet$ sudo ./step-1.sh
Testing root access...
uid=0(root) gid=0(root) context=u:r:init:s0

PL version: 5 (5)
LK version: 2 (2)
TZ version: 263 (263)

Your device will be reset to factory defaults...
Press Enter to Continue...

Dumping GPT
tmp-mksh: dd if=/dev/block/mmcblk0 bs=512 count=34 of=/data/local/tmp/gpt.bin: not found
tmp-mksh: chmod 644 /data/local/tmp/gpt.bin: not found
204 KB/s (17408 bytes in 0.083s)

Modifying GPT
[2019-05-10 15:40:29.366324] Input GPT:
[2019-05-10 15:40:29.376146]
[2019-05-10 15:40:29.376342] Sector size (logical): 512 bytes
[2019-05-10 15:40:29.376453] Disk identifier (GUID): 04EF21A7-28FA-4D1D-A17E-B450CE093E4F
[2019-05-10 15:40:29.376527] Partition table holds up to 128 entries
[2019-05-10 15:40:29.376602] This partition table begins at sector 2 and ends at sector 33
[2019-05-10 15:40:29.376666] First usable sector is 34, last usable sector is 61071326
[2019-05-10 15:40:29.376727] Other partition table is at sector 61071359
[2019-05-10 15:40:29.376785]
[2019-05-10 15:40:29.376899] Number Start (sector) End (sector) Size Name
[2019-05-10 15:40:29.389570] 1 1024 7167 3.00 MiB proinfo
[2019-05-10 15:40:29.390903] 2 7168 16383 4.50 MiB PMT
[2019-05-10 15:40:29.391916] 3 16384 18431 1024.00 KiB kb
[2019-05-10 15:40:29.392886] 4 18432 20479 1024.00 KiB dkb
[2019-05-10 15:40:29.393976] 5 20480 22527 1024.00 KiB lk
[2019-05-10 15:40:29.395107] 6 22528 32767 5.00 MiB tee1
[2019-05-10 15:40:29.396019] 7 32768 43007 5.00 MiB tee2
[2019-05-10 15:40:29.396844] 8 43008 123903 39.50 MiB metadata
[2019-05-10 15:40:29.397642] 9 123904 124927 512.00 KiB MISC
[2019-05-10 15:40:29.398455] 10 124928 141311 8.00 MiB reserved
[2019-05-10 15:40:29.399282] 11 141312 174079 16.00 MiB boot
[2019-05-10 15:40:29.400118] 12 174080 208895 17.00 MiB recovery
[2019-05-10 15:40:29.402713] 13 208896 3515391 1.58 GiB system
[2019-05-10 15:40:29.403689] 14 3515392 4383743 424.00 MiB cache
[2019-05-10 15:40:29.404483] 15 4383744 60619775 26.82 GiB userdata
[2019-05-10 15:40:29.405264] 16 60619776 60845055 110.00 MiB boot_tmp
[2019-05-10 15:40:29.406056] 17 60845056 61070335 110.00 MiB recovery_tmp
[2019-05-10 15:40:29.485583]
[2019-05-10 15:40:29.485762] Regenerate primary and backup GPT from input
[2019-05-10 15:40:29.485931] Writing regenerated GPT to gpt/gpt.bin.gpt
[2019-05-10 15:40:29.486147] Writing regenerated backup GPT to gpt/gpt.bin.bak
[2019-05-10 15:40:29.486273] Writing backup GPT offset to gpt/gpt.bin.offset
Traceback (most recent call last):
File "modules/gpt.py", line 323, in <module>
main()
File "modules/gpt.py", line 277, in main
part_list_mod1 = modify_step1(part_list)
File "modules/gpt.py", line 181, in modify_step1
assert partition['name'].decode("utf-16le").rstrip("\x00") == "userdata", "the last partition is not userdata, refusing modification"
AssertionError: the last partition is not userdata, refusing modification
dragon@dragonfire:~/amonet-suez2/amonet$

Here is the output from the last bricked one I have (the one that we've been trying to troubleshoot. This is the one we've been talking about. this output is from bootrom-step):

dragon@dragonfire:~/amonet-suez2/amonet$ sudo ./bootrom-step.sh
[2019-05-10 15:46:03.137463] Waiting for bootrom
[2019-05-10 15:46:35.804536] Found port = /dev/ttyACM0
[2019-05-10 15:46:35.809408] Handshake
[2019-05-10 15:46:35.810115] Disable watchdog

* * * Remove the short and press Enter * * *

[2019-05-10 15:46:42.484572] Init crypto engine
[2019-05-10 15:46:42.503524] Disable caches
[2019-05-10 15:46:42.503981] Disable bootrom range checks
[2019-05-10 15:46:42.539877] Load payload from ../brom-payload/build/payload.bin = 0x4820 bytes
[2019-05-10 15:46:42.543361] Send payload
[2019-05-10 15:46:43.082949] Let's rock
[2019-05-10 15:46:43.083695] Wait for the payload to come online...
[2019-05-10 15:46:43.087653] all good
[2019-05-10 15:46:43.087948] Check GPT
Traceback (most recent call last):
File "main.py", line 192, in <module>
main()
File "main.py", line 95, in main
switch_user(dev)
File "main.py", line 56, in switch_user
block = dev.emmc_read(0)
File "/home/dragon/amonet-suez2/amonet/modules/common.py", line 196, in emmc_read
raise RuntimeError("read fail")
RuntimeError: read fail
dragon@dragonfire:~/amonet-suez2/amonet$

Here is from bootrom-step-minimal (which goes all the way and reboots to white amazon logo that's NOT hacked fastboot.)

dragon@dragonfire:~/amonet-suez2/amonet$ sudo ./bootrom-step-minimal.sh
[2019-05-10 15:48:46.666144] Waiting for bootrom
[2019-05-10 15:49:04.272576] Found port = /dev/ttyACM0
[2019-05-10 15:49:04.277535] Handshake
[2019-05-10 15:49:04.278470] Disable watchdog

* * * Remove the short and press Enter * * *

[2019-05-10 15:49:12.477079] Init crypto engine
[2019-05-10 15:49:12.496180] Disable caches
[2019-05-10 15:49:12.496675] Disable bootrom range checks
[2019-05-10 15:49:12.508945] Load payload from ../brom-payload/build/payload.bin = 0x4820 bytes
[2019-05-10 15:49:12.512370] Send payload
[2019-05-10 15:49:13.058863] Let's rock
[2019-05-10 15:49:13.059579] Wait for the payload to come online...
[2019-05-10 15:49:13.063487] all good
[2019-05-10 15:49:13.063785] Running in minimal mode, assuming LK and TZ to have already been flashed.
[2019-05-10 15:49:13.063877] If this is correct (i.e. you used "brick" option in step 1) press enter, otherwise terminate with Ctrl+C

[2019-05-10 15:49:31.613151] Check GPT
[2019-05-10 15:49:33.254087]
[2019-05-10 15:49:33.254344] Sector size (logical): 512 bytes
[2019-05-10 15:49:33.254494] Disk identifier (GUID): 04EF21A7-28FA-4D1D-A17E-B450CE093E4F
[2019-05-10 15:49:33.254586] Partition table holds up to 128 entries
[2019-05-10 15:49:33.254682] This partition table begins at sector 2 and ends at sector 33
[2019-05-10 15:49:33.254771] First usable sector is 34, last usable sector is 61071326
[2019-05-10 15:49:33.254881] Other partition table is at sector 61071359
[2019-05-10 15:49:33.254963]
[2019-05-10 15:49:33.255104] Number Start (sector) End (sector) Size Name
[2019-05-10 15:49:33.256995] 1 1024 7167 3.00 MiB proinfo
[2019-05-10 15:49:33.258224] 2 7168 16383 4.50 MiB PMT
[2019-05-10 15:49:33.259282] 3 16384 18431 1024.00 KiB kb
[2019-05-10 15:49:33.260076] 4 18432 20479 1024.00 KiB dkb
[2019-05-10 15:49:33.260878] 5 20480 22527 1024.00 KiB lk
[2019-05-10 15:49:33.261695] 6 22528 32767 5.00 MiB tee1
[2019-05-10 15:49:33.262512] 7 32768 43007 5.00 MiB tee2
[2019-05-10 15:49:33.263344] 8 43008 123903 39.50 MiB metadata
[2019-05-10 15:49:33.264162] 9 123904 124927 512.00 KiB MISC
[2019-05-10 15:49:33.264982] 10 124928 141311 8.00 MiB reserved
[2019-05-10 15:49:33.266111] 11 141312 174079 16.00 MiB boot_x
[2019-05-10 15:49:33.267252] 12 174080 208895 17.00 MiB recovery_x
[2019-05-10 15:49:33.268328] 13 208896 3515391 1.58 GiB system
[2019-05-10 15:49:33.269225] 14 3515392 4383743 424.00 MiB cache
[2019-05-10 15:49:33.270231] 15 4383744 60619775 26.82 GiB userdata
[2019-05-10 15:49:33.271215] 16 60619776 60845055 110.00 MiB boot
[2019-05-10 15:49:33.272040] 17 60845056 61070335 110.00 MiB recovery
[2019-05-10 15:49:33.351518]
[2019-05-10 15:49:33.351792] Check boot0
[2019-05-10 15:49:34.863629] Check rpmb
[2019-05-10 15:49:35.070287] Clear preloader header
[8 / 8]
[2019-05-10 15:49:36.704283] Downgrade rpmb
[2019-05-10 15:49:36.704615] Recheck rpmb
[2019-05-10 15:49:37.598700] rpmb downgrade ok
[2019-05-10 15:49:37.598978] Inject payload
[1 / 1]
[807 / 807]
[1 / 1]
[807 / 807]
[2019-05-10 15:50:04.405334] Force fastboot
[2019-05-10 15:50:05.976991] Flash preloader
[361 / 361]
[353 / 353]
[2019-05-10 15:50:18.038037] Reboot to unlocked fastboot
dragon@dragonfire:~/amonet-suez2/amonet$ sudo ./fastboot-step.sh
Your device will be reset to factory defaults...
Press Enter to Continue...

< waiting for any device >