You may find many foreign packages (Debian/Ubuntu) that work; however, many will not. This is because of incompatible libraries. You may be more successful if your foreign packages are released close to the build date of the Fatdog64 version you use. For example the Fatdog 500 series (500, 510, 520/521) build date is 2009, so for Debian this would be Etch or Lenny. For the Fatdog64 600 series (released in 2012), you may be able to use Debian Squeeze. The 700 series is near in time to Debian Jessie, and the 800 to Debian Stretch.
Even then this may not work, because of missing software libraries or how libraries are compiled differently in Fatdog. You can try to extend your luck by also installing the missing libraries as well from your foreign package source, but this is pushing it.
If you still cannot get it to work, you might try using either a similar package from Fatdog64 repository, or compiling that package from source.