You will need the specific ROM and recovery images for your device variant.
The actual operating system build (look for LineageOS 17.1, 18.1, or higher depending on port stability).
You need to gather the correct files for your specific KEY2 variant. Because LineageOS support for the KEY2 is driven by the community, look for the official or highly rated unofficial build threads on XDA Developers.
Modifying system software voids any remaining manufacturer warranty.
I can provide the specific download paths and compatibility checks for your exact hardware version. Share public link
If you require root access, you can sideload the Magisk zip file using the custom recovery environment following the same steps used for GApps.
On your KEY2, go to Settings > System > About Phone . Tap Build Number seven times until a message says developer options are active.
Upgrading your BlackBerry KEY2 to LineageOS breathes new life into the phone. It provides modern privacy controls, a cleaner interface, and a much newer Android framework. This guide covers everything you need to know to safely install LineageOS on your BlackBerry KEY2. Important Prerequisites and Warning
Decided to go back to the stock BlackBerry OS? You can revert your device. The safest way to return to the original firmware is to re-run the you used earlier. This will completely overwrite LineageOS and restore the stock BlackBerry Android 8.1 system.
As an unofficial beta release, LineageOS 22.2 on the KEY2 is not perfect. Knowing its limitations ahead of time will save you frustration.