Would you use Guile to run it on FreeBSD? I haven't tested Akku on FreeBSD, only on Linux and macOS, so I wouldn't count on it working without some fixes first.
FreeBSD currently has:
- Chez 9.5: https://www.freshports.org/lang/chez-scheme/
- Petite Chez 8.4: https://www.freshports.org/lang/petite-chez/
- Guile 1.8 as 'guile': https://www.freshports.org/lang/guile/
- Guile 2.0.14 as 'guile2': https://www.freshports.org/lang/guile2/
I haven't done any real work with any of these, so can't say for sure.