There is no simple software exploit to unlock the bootloader on the latest firmware versions. Hardware-based exploits (such as shorting points on the motherboard using a Linux environment) have been used in developer communities, but they carry a high risk of permanently bricking the device.
Run the community bootloader unlock script (available on XDA Developers). amazon fire hd 8 10th generation custom rom top
Where to find builds and support
A lightweight, completely open-source Android ROM that strips away every trace of Amazon. There is no simple software exploit to unlock
Do you have access to a computer running or a live USB environment? amazon fire hd 8 10th generation custom rom top
Help you find a guide for installing a (like Nova) on the Fire Tablet.