If you have accepted these risks and still wish to proceed (perhaps with a device you are willing to sacrifice for the sake of experimentation), the general process would look like this.
You may need to use tools to patch the boot.img or vendor.img . blackberry keyone custom rom top
The vast majority of carrier-branded and global variants of the KEYone (such as the BBB100-1, BBB100-2, and BBB100-3) feature a strictly locked and un-bypassable bootloader . If your bootloader cannot be unlocked, you cannot install a custom ROM. If you have accepted these risks and still
You MUST unlock your bootloader. This is the biggest hurdle for BlackBerry devices. If your bootloader cannot be unlocked, you cannot
Slightly heavier on the device's limited RAM compared to LineageOS. 3. AOSP / Phh-Treble Generic System Images (GSIs)
Flashing a ROM completely wipes your internal storage. Backup photos, contacts, and 2FA tokens.