For the , also known as the 2020 model (codenamed "onyx"), the current consensus among the modding community is that there is no verified custom ROM available because the bootloader cannot be unlocked.
Unlike older models (such as the 8th Gen), which had hardware exploits to bypass security, the 10th Gen remains locked. 🛑 The "Locked Bootloader" Reality
The process to unlock the bootloader varies by device. For the Fire HD 8, you might need to use specific commands via ADB and possibly a tool designed for your device. Be cautious, as unlocking the bootloader can void your warranty and potentially brick your device.
Attempting to force a custom ROM designed for older models onto a 10th Gen device will cause a permanent malfunction or "brick". Alternatives for 10th Gen Users