Unsupported firmware

If you don't have the required firmware follow this guide

1. Install 7-Zip Zstd
2. With 7-Zip Zstd Open AP archive from your stock firmware (if you don't have it then download it on samfw.com)
3. Open super.img.lz4 inside AP archive
4. Drag vendor.img out of super.img.lz4 to desktop (or anywhere else)
5. Follow flash steps from ROM post (but don't reboot)
6. Reboot to fastboot (adb reboot fastboot)
7. Flash vendor.img using fastboot (fastboot flash vendor vendor.img)
8. Reboot