The following article talks about currently limited support in Ghost Solution Suite (GSS) for SecureBoot mode for Linux clients.
GSS 3.3 RU11
Starting with GSS 3.3 RU11 release, GSS has limited support for SecureBoot mode for Linux clients.
Limitations:
Considering the limitations above, it’s recommended to configure a separate PXE server for Linux clients to avoid conflicts or network boot time increase for Windows clients.
There are some additional steps that need to be performed manually:
In addition to PXE boot, boot media created with LinPE now also supports SecureBoot.