Instead of using SMB to transfer files into a Windows Server Core instance, why not use SCP over SSH?
Get-WindowsCapability -Online | ?{$_.Name -Like 'openssh*'}
Example output:
Name : OpenSSH.Client~~~~0.0.1.0
State : Installed
Name : OpenSSH.Server~~~~0.0.1.0
State : NotPresent
Add-WindowsCapability -Online -Name OpenSSH.Server~~~~0.0.1.0
Start-Service sshd
Set-Service sshd -StartupType 'Automatic'
Get-NetFirewallRule -Name *ssh*
Example output:
Name : OpenSSH-Server-In-TCP
DisplayName : OpenSSH SSH Server (sshd)
Description : Inbound rule for OpenSSH SSH Server (sshd)
DisplayGroup : OpenSSH Server
Group : OpenSSH Server
Enabled : True
Profile : Any
Platform : {}
Direction : Inbound
Action : Allow
EdgeTraversalPolicy : Block
LooseSourceMapping : False
LocalOnlyMapping : False
Owner :
PrimaryStatus : OK
Status : The rule was parsed successfully from the store. (65536)
EnforcementStatus : NotApplicable
PolicyStoreSource : PersistentStore
PolicyStoreSourceType : Local