[Fire HD 6 and 7 General] thallat:
I tried posting this reply in your original thread, bibikalka, but can't figure out if it actually worked as the supposed page where the post exists won't load. Maybe something to do with newbie posting restrictions. Speaking of, if XDA is going to restrict links posted by newbies, it'd be nice of them to include an easy obvious tool to strip them out after I already typed a long post containing multiple links.

First off, thanks so much, bibikalka, for everything you've done on this topic so far!

So I finally had enough of my Fire's crappy stock file management (somewhat mysterious and ever growing "Miscellaneous Others" category that there is no easy way to reduce) and decided to root. Thought for sure I had all of my bases covered when I started, but didn't realize until getting to the point of flashing back up to latest stock system, recovery, and bootloader that 5.4.0.1 was the last confirmed success and since I was allowing OTAs up until today, I must have been updated all the way to 5.6.0.1 before I flashed down to 4.5.3. Before I go any further, I'm hoping for some guidance on what to flash next.

What I've done so far:

1. Started with stock, relatively freshly factory reset, Fire HD 6, which as I said, should have been 5.6.0.1 (no, I didn't absolutely positively double check this before I started, but I remember an OTA system update pretty recently, so should be latest, which is 5.6.0.1 according to: amazon.com/gp/help/customer/display.html?nodeId=201596860 ).

2. Enabled ADB on Fire and computer (which FWIW, I'm doing all this from my LXLE Eclectica 16.04.2 64bit).

3. Booted to stock recovery using "adb reboot recovery" and entered "Apply update from ADB" state from the stock recovery menu.

4. Sideloaded 4.5.3 rollback using "adb sideload update-kindle-20.4.5.3_user_453011120.bin" (file gotten from: kindle-fire-updates.s3.amazonaws.com/update-kindle-20.4.5.3_user_453011120.bin ).

5. After successful sideload, I performed a "wipe data/factory reset" and then a "reboot system" using the stock recovery menu.

6. Completed initial boot setup, skipping getting connected to WiFi.

7. Sideloaded jmzFireHDTool using "adb install JmzFireHDTool_v4.apk" (downloaded from : mega.nz/#F!qswxVQSb!E8NTrib3QYZU3ztlylbgmg ), and then disabled OTAs with it.

8. Sideloaded Kingroot using "adb install NewKingrootV5.2.2_C184_B435_en_release_2017_09_20_20170920220117_105203.apk" (also downloaded from : mega.nz/#F!qswxVQSb!E8NTrib3QYZU3ztlylbgmg , connected to local WiFi, and then let it run it's various system optimizations before requesting root, which didn't seem to even try to work let alone work.

9. Realized there was a newer Kingroot and sideloaded using "adb install -r NewKingrootV5.3.3_C193_B445_en_release_2018_01_23_20180124192653_105203.apk" (downloaded from: kingroot.net ), let it update some optimizations, and then requested root again. This time root succeeded.

10. Sideloaded Flashify using "adb install com.cgollner.flashify_1.9.2-64_minAPI14.apk" (downloaded from: mega.nz/#F!qswxVQSb!E8NTrib3QYZU3ztlylbgmg ).

11. Used Flashify to backup stock recovery and then flash TWRP 2.8.6.0-ariel (downloaded from: mega.nz/#F!qswxVQSb!E8NTrib3QYZU3ztlylbgmg and copied to Fire using "adb push -p openrecovery-twrp-2.8.6.0-ariel.img /sdcard/Download").

12. My Fire then rebooted into TWRP successfully (I didn't explicitly give a command to do so. I'm assuming Flashify defaults to rebooting into a recovery after flashing it.)

13. Started copying zip files needed for next step to Fire using "adb push" command. This is when I realized I wasn't sure what I was doing ;)

What bootloader do I need to flash given my Fire should have taken all OTA system updates to 5.6.0.1?

Does the system version I choose affect that? I honestly hadn't 100% decided if I was going to go back to Fire OS rooted (5.6.0.1, I guess) or try CM11.

Assuming I do stay with Fire OS, can anyone confirm gapps are working with latest 5.6.0.1? If not, what are my other options?

Thanks in advance for any and all help!