Error "Function not implemented" when creating symbolic link
The filesystem you're trying to create the symbolic link on doesn't support symbolic links. All the native Linux filesystems (ext2-4) support symlinks, but the DOS filesystem used on SD cards doesn't, and several others don't. For a filesystem implemented with FUSE (as in this case), it's entirely up to the filesystem driver, so you can't tell whether it supports symlinks or not without trying. You won't be able to create symlinks on those filesystems.