GitHub blocks files larger than 100 MiB. Therefore, if you are migrating a repository with objects larger than 100 Mib to Github, you'll need to migrate those large objects to LFS.
By default, windows and mac do not have a case sensitive filesystem. For this reason, I recommend using linux for lfs migration. Also, if the lfs migration seems to take a long time, this is often due to lots of disk I/O. To speed things up, use a cloud linux instance with max disk I/O.
Make sure you have git-lfs installed.