[ixtab]

Use this combination of kernels and images:
- diags (these can both be flashed from fastboot):
diags_kernel 5.0.0 (the ge.tt one)
mmcblk0p2_ssh 5.0.1 (the ge.tt one)
- main:
main kernel 5.1.2 (make sure to flash it from fastboot!)
either of the "mmcblk0p1 5.1.2" images (must be dd'ed from diags). The first is pristine, the second already includes Jailbreak, Kindlet Jailbreak, and SSH.

The procedure you took looks *almost* correct to me, except that you need to flash *both* kernels to the correct respective location, and the diags image as well.

The final commands to execute in diags are
"idme -d --bootmode main", then "reboot", not "idme -d --bootmode", then "main reboot". But that probably just was a typo on your part.

The images and kernels I mentioned above are guaranteed to work. I debricked my device several times with them (in fact, I am the one who created the 5.1.2 image and kernel).

PS: Your description looks like you either flashed a broken main kernel, or a wrong one. (Yes, there are "known broken" kernels in the list! The 5.1.2 is "known good", though). Thus, make sure to flash the correct main kernel to the correct location! This is probably the step that you did wrong so far.
PPS: You don't need to re-flash the diags kernel and image over and over. As soon as diags works and you can access it with SSH, you can leave the diags parts of the device alone, and focus on the main kernel and image.