It looks like it's possible to run the vendor RKLLM/RKNN NPU stack, which normally only works on Rockchip's older 6.1 BSP kernel. Kiln manages to run the same stack on a clean mainline Linux 7.1.3 kernel instead:
https://github.com/gahingwoo/kiln
There's also another effort to get it running on a fully open-source stack, although with only partial success. Single-task INT8 Conv2D operations are now byte-for-byte identical to the CPU implementation, but multi-task execution remains the main challenge:
https://github.com/flipperdevices/flipperone-linux-build-scripts/issues/55