One issue we've had with FreeFileSync is that the 'portable' functionality of it is a paid-only feature. As are removing ads. We'd rebuild it ourselves and rename it if needed, but the source code requires patched libraries and has no/incomplete build instructions. Neither I nor anyone else I know was able to get it to build, at least over the many years I played with it. That's why the version we make available at PortableApps.com is still version 6.2, that last version that didn't purposely break portability.