Recommended Solution for WireGuard + Xcode 16 Compatibility Issues
After extensive troubleshooting, the only solution that worked was replacing the official WireGuard dependency with this forked and patched version:
https://github.com/groupofstars/wireguard-apple
Why This Works:
The official WireGuard package can't be modified (SPM restrictions)
The fork explicitly resolves critical build errors in Xcode 16 (e.g., u_int32_t, _char type declarations).
Addresses module interoperability issues between Swift and WireGuard's C code.