Thanks to everyone maintaining various things for this and adding instructions along the way.
Just to help others in 2022-2023 to the Fire HD10 2017
This has been lost in time on this thread but you CAN still root with 5.7.0.0 you just CANNOT use mtk-su because it's been patched against so the instructions are outdated, hence the confusion when it errors-out.
But you MUST root before you can install TWRP, there is no other way, otherwise you get all the errors.
You need to go to a far more manual exploit, it looks tedious but you only have to do it once and maybe 10-15 minutes tops once you have a working ubuntu live usb or virtual install
Read this whole guide before starting. This is for the 7th gen Fire HD10 (suez). Current version: amonet-suez-v1.1.2.zip NOTE: This process does not require you to open your device, but should something go horribly wrong, be prepared to do...
forum.xda-developers.com
This root method is nice because it's all offline, no wifi needed.
Very very hard to brick the HD10 which is nice, I got into a bootloop at first try but even Amazon's own ADB sideload will still take the stock image from their website and recover, just tedious.