Most install options are described within the Autodesk Account custom install user interface. Here is some additional information about the security settings and Express Tools options that are available when you are creating a standalone custom install or deployment.
It's AutoCAD telling you the file you opened is from AUTOCAD, and not a 3rd party CAD file. Is there something else going on that you did not mention that is slowing you down getting into a file?

To fully interoperate with the ECA PKI, users must import the ECA Root and ECA subordinates CA certificates into their trust store. The latest certificates may be installed automatically by using InstallRoot. Below are instructions to perform this installation for different popular browser versions on Windows Operating Systems.

This particular example perfectly highlights why Fragmented Trust Cad Install is so captivating.
When creating a Custom Install versus a Deployment, both the device creating the image and the destination are the same, and it is easier to support symbolic links on the same device. Further, the image creation tool can enable symbolic links on the device if they are not already enabled.

Two malicious versions shipped a remote access trojan via npm install. The attack window was about 3 hours before the community caught it. This triggered a bunch of conversation, including...
Tools & Configuration Files Tools