A creative workaround for the locked bootloader: Run a different Android OS inside the stock OS.
The lack of custom development is due to three primary factors:
Even if the bootloader were unlocked, the Snapdragon 808 has no vendor support beyond Android 7.1. Qualcomm dropped 3.10 kernel updates in 2017. Backporting a modern kernel (4.9+) would require thousands of hours of work to reimplement BlackBerry’s proprietary:
No developer owns a Priv anymore. The device is legacy unsupported.