@rhessinger
Thanks for digging into this, Rich. Here's our actual Samba config:
Samba version: 4.15.13-Ubuntu
Topology: single domain, single DC, single site — progetpoc.local (netbios PROGETPOC), DC dc1.progetpoc.local, site Default-First-Site-Name. No second domain, no trusts, no additional sites.
Domain/forest functional level: Windows 2008 R2 (the oldest Samba supports) — never raised to a modern level.
ProGet directory config: "Domain controller host" set to a single bare IP (Samba's Docker gateway IP), connection type "Use LDAPS and bypass certificate errors" (self-signed cert, since this is a throwaway test domain).
The thing that stands out to me: this is a single domain / single DC / single site setup — there's no second domain or trust relationship for a query to genuinely need to "refer" to. So on paper there shouldn't be anything to refer to, yet we still consistently get LdapReferralException on the group-membership resolution path specifically (not on basic user/group lookups, which we confirmed work fine). That makes me wonder if this is less about real cross-domain referrals and more about how Samba responds for a specific naming context (Configuration/Schema partition?) during whatever query ProGet's authorization path issues for recursive group membership — rather than a genuine multi-domain referral case like your local test environment might've had.
Happy to grab a full LDAP trace/packet capture of the exact failing query if that would help narrow it down further. Also worth asking: was your local Samba 4 test also a single-domain/single-DC setup, or did it include a trust/second domain? If yours was multi-domain and ours isn't, that might explain why you're not seeing the same exception.