GhostBSD does not support your video gpu by default. This decision is to minimize the ISO size. However, I have created an ISO that supports your older Nvidia gpu. I do not have a T420 to test the ISO with. Here's the location of the file, https://link.storjshare.io/s/jut2wiuhynoln2v5z4mbcpiikl4a/g...

New to BSD so sorry for the noob question, but I get an error that no screens are found and then it defaults to shell.