Comment 1 for bug 1806035

From https://docs.fedoraproject.org/en-US/fedora/f29/release-notes/sysadmin/File_Servers/:
"""
Finally, Samba 4.9 differentiates between anonymous and guest access via SMB protocol. A side effect of this is that it is now required to have a mapping for BUILTIN\Guests group. The mapping can be provided automatically if a default identity backend allows to create entries on demand. Alternatively, net utility can be used to provide a group mapping for BUILTIN\Guests via

net groupmap add sid=S-1-5-32-546 unixgroup=nobody type=builtin
"""

(it would be "nogroup" in ubuntu/debian)