Windows 8.1 reached its official End of Life (EOL) in January 2023. It no longer receives security patches. The Recommended Alternative: Windows 11 ARM64
Deploying to older developer boards or specific early ARM64 smartphones (via community projects like Lumia WoA). Step 1: Sourcing the Windows 8.1 ARM64 ISO windows 81 arm64 iso install
Before investing time into this setup, consider the severe limitations of running Windows 8.1 on ARM hardware: Windows 8