Success! Just loaded the 2020 maps. A few notes:
The links I used were:
1b file:
https://www.e90post.com/forums/showthread.php?t=1461515
2020 Maps:
https://www.e90post.com/forums/showthread.php?t=1654612
FSC Generator:
https://www.e90post.com/forums/showthread.php?t=1453464
https://ufile.io/nj2ttwoc
For loading the maps onto the USB drive, there should be a "pkgdb" folder and a "config.nfm" file - I accidentally extracted one file directory higher, and it didn't work at first. If you plug the USB drive in before you start the car, it automatically prompts for an update.