Firetv

Exploit Patch Launcher Manager

Download & install Launcher Manager app (v1.1.1).
Downloader code: 2370884
Through ADB run the following command to give it the required permissions:
pm grant com.wolf.tn android.permission.WRITE_SECURE_SETTINGS

pm grant com.wolf.tn android.permission.WRITE_SECURE_SETTINGS

Source XDA Forum Tools

Manual Instructions through ADB

Enable ADB debugging in FireOS
FireOS Settings > My Fire TV > Developer options > ADB debugging > on

NOTE: If Developer options isn't showing, open About, select Fire TV [Cube/Stick] and tap select 7x to unhide developer menu.

Reset blacklist apps

settings delete global hidden_api_blacklist_exemptions

Disable OTA firmware

Disable OTA firmware updates [FIRE TV]

pm disable com.amazon.device.software.ota
pm clear com.amazon.device.software.ota
pm disable com.amazon.device.software.ota.override
pm disable-user com.amazon.sneakpeek
pm disable com.amazon.client.metrics
sync

NOTE: verify com.amazon.device.software.ota is still disabled after rebooting. List all disabled apps:

pm list package -d

Set a custom launcher

[FIRE TV]

pm disable com.amazon.firehomestarter
pm disable com.amazon.tv.launcher

Press Home button on remote, select your installed custom launcher from the popup at the buttom of the screen.

NOTE: You will no longer be able to access FireOS settings after disabling Amazon Launcher