You can unlock the bootloader of the 2018 Fire HD 8 if you force it into download mode by opening it up and shorting the CLK test point to ground. Older tablets don't need to be opened up, it's all just software. Everything after that though has been unable to have the bootloader unlocked.
Ignorant Q: Could one ostensibly replace the ROM? Surely there has to be some Chinese company that can get you a custom ROM built and replace it on the device?
EDIT: Yes, I meant physically de-solder/replace of the ROM - is that a nightmare?
What if you could find the economics of having people ship you their devices and either donating (to schools (NOT UNIVERSITY SLURPS)) or paying for their device to be up-ROM'd or e-cycled?
(My first job as a freshman in Highschool was desoldering ROMs and soldering new ROM chips into the boards of Amigas and Apple ][e's -- I had tons of these new ROMs on a strip and in tubes - but I never had any use for them... I with I had kept them.)
((Also, just to let you know the difficulty level - replacing a ROM chip on an Apple ][e etc was as simple as receiving an instruction set:
"Desolder the red guys. Resolder with these green guys."
That was the extent of my knowledge to ROMs in ][Es
The (boot)ROM is on-die, within the CPU, there's no way to replace it.
You can potentially replace the OS image (confusingly, often referred to as a "ROM") on the flash storage, but unless the bootloader agrees to boot it (either due to it being signed correctly, or due to the bootloader being unlocked) you're SOL.
Probably not, most devices have the first stage boot loader on read only memory that is locked using an e-fuse. You would need to physically modify the device to change it.
FWIW, I had an older Fire tablet that I had loaded Android onto and it wasn’t great. It would crash randomly and the battery life was awful. These days I have a newer Fire tablet. It’s a few years old now but I still use it all the time for reading e-books from the library, and I have a few Android apps loaded onto it that I use for working on my car and they all work fine. In other words, there’s not really any reason to reflash them, the stock OS is fine.
