[Samba] SMB share access for machines which are not joined to the domain?

[Goetz, Patrick G]

Samba 4.7.6 running on Ubuntu 18.04, with host joined to an AD domain as 
a domain member.

I have all this working perfectly for SMB clients which are joined to 
the domain, however I need to provide SMB access (if possible) to a 
handful of machines that are not domain members and can't be made domain 
members.  Is there any way to do this?

I thought configuring "allow hosts" in smb.conf with the IP addresses of 
the 2-4 machines in question might work, but this seems to restrict all 
access, in particular blocking domain-joined clients when configured.