Assuming you have the Steam version, If you have the hard drive space, I recommend copying the Packages subdirectories to another spot, that’s the bulk of the 100 GB download (actually about 98 or so), this will save you the interminable re-download and potentially any hiccups therein. You just need to move it back into the same spot it came from when you finish the initial 500MB install of the base program and it starts to download the 100GB. Stop the program when it starts the 100GB download, move the Packages back where it was before, restart the sim, it should recognize the packages with minimal updates downloaded thereafter.
Not sure if this trick works for FS bought through the MS Store. But that’s how all the reviewers got to distribute launch day copies quickly to multiple PC rigs for analysis.