[Kindle Fire HDX 7" & 8.9" Q&A, Help & Troubleshoot] zekzekzek:
Hi everyone - I have a Kindle Fire HDX Thor device and I've been searching for some time and have made a detailed post here about my progress thus far with unlocking the bootloader (successfully). My next step is to flash a rom. This is where I am stuck.

I have TWRP 3.1.1-1

I have confirmed that my bootloader is unlocked.

I now have Lineage 14.1 ready to go (lineage-14.1-20220317-UNOFFICIAL-thor.zip) from this thread:

https://xdaforums.com/t/rom-apollo-thor-lineage-14-1-17-mar-2022.4398657/

I can access fastboot and TWRP just fine but looks like ADB commands do not work. I do see "Android ADB Interface" in Device Manager and can run [fastboot -i 0x1949] commands.

My question is: how do I transfer the Lineage 14.1 rom to my device?

In TWRP, I have tried sideload, mount usb, enable MTP and none of these do anything. I feel like I'm missing something and just not sure what at this point.

Thank you!

UPDATE 1: Lineage 14.1!

Impatience keeping me searching and thinking of new things to try for problem solving.

I was sifting through posts and understood that not having my Kindle device show up on my PC as an accessible drive meant that I have an ADB drivers problem. Thus the hunt began for drivers that would work. I tried Motorola, I tried official kindle drivers, I tried a bunch of Android drivers as well but nothing seemed to work. Usually the drivers would just install and nothing would happen or I'd get an error saying my drivers were not 64 bit.

Okay then, let's get 64 bit drivers. After some more searching, I stumbled upon this site:

https://android-file.com/usb_driver_r13-windows

I downloaded and updated drivers through Device Manager and lo and behold! It worked! The kindle device showed up on my PC. Who knew.

Now that my Kindle device shows up, I was able to copy and paste Lineage 14.1 to the device and then install from TWRP. After going through setup screens, the tablet looks SWEEET.

I wanted to install Gapps and figured I should restart the tablet before proceeding with installing so it could do any sort of cleanup if needed. But now, on restarting, I'm stuck on the Lineage animation. Pretty sure I read some post about this issue so back to searching now.

UPDATE 2: All good...mostly

I kept searching and found this here by @DB126. I followed these instructions and it worked. I'm no longer stuck on the boot animation for Lineage 14.1 and went on to the next item.

Next step was to get Google Play Store. I see there are two methods to doing this. One is Gapps and the other is MicroG. I went with MicroG since I read that it had a significant performance boost over Gapps. I installed MicroG by following this thread:

[MOD][FLASHABLE] microG unofficial installer

Description microG unofficial installer simplify the installation of microG. IT FEATURE ALSO NON-AROMA LIVE SETUP (now working on all phones). Download microG unofficial installer v1.3.1 beta - Full (Android 2.2 - 13) - MIRROR microG unofficial...

xdaforums.com

All good from my end. Gmail app isn't working but I'm able to install apps just fine. Still playing around with it but looks like the main challenges are done.