I have been tasked to remove an external SharePoint server that resides in our DMZ from the domain. Can I do this? I know the implications of our domain users no longer being able to access the site with their domain credentials but are there other alternatives to accomplish this scenario? Is there supporting documentation to support or advisement against doing so? We have the server sort of "locked down" by restricting by IP address but now our security team wants it removed totally from the domain as it is a security risk to our domain by sitting out there in the DMZ.
Running SharePoint in a workgroup may be possible (on some versions, with some messing about), but it's definitely not a supported configuration. So best to run with 'SharePoint requires a domain to operate'.
So that said, you probably have 2 choices: