Not NFS, but I have Borg repos created and used on my Mac, subsequently turned into Borg special remotes for access by a Linux machine. Trying to get file contents from there sometimes fails because I did not think to ignore xattrs while creating the archive, and these particular Apple xattrs-shenanigans aren't compatible with the extracting machine's filesystem (btrfs). borg extract has a --noxattrs option which I thought might be useful in general for git-annex, since all one usually wants is the actual file contents. Perhaps this could be implemented as a configuration parameter or otherwise passed somehow?