I am not sure if this is the right place to ask about this.
I am on windows 10 using the 6.0 rc nightly. If I try to use the footprint generator with the SOIC package it errors out instantly. All other packages seem to work.
I can not really offer any advice other than maybe open a bug report over at launchpad. (It might be that some python requirements are missing in the nightly build installations.)
There are also alternative footprint generators available. The one we use for the official library is standalone at this point in time. A footprint definition is done using yaml files (text based, for examples look under the size definition folder. It takes the dimensions of the package and creates a footprint according to IPC rules. The generated footprint might differ slightly from the datasheet suggested one as the datasheet might use older IPC standards or might not even use these standards at all.)