Migrate users to new server

SYSTEM INFORMATION
OS type and version Centos 7.9
Webmin version 2.0

I want to migrate users from Centos 7 to RHEL9 using Webmin Users Export and Run batch file.
When creating the batch file Webmin creates a file with the format Username:password:UID:GID etc

When this is imported by running the batch file, it then creates a group name with the GID instead of the original group name which in my case is the same as the username.

Can the format of the batch file be configurable? I would actually like to have a blank UID so that new ones are created and have the group name match the user name.

As this is just for a pass through mail server, I don’t need home directories etc either, though I want to keep the /sbin/nologin field.

Any help appreciated.

Can anybody help with this?