Once again, the GSSAPI/Kerberos is enabled by default. There's no difference between the GUI and the .NET assembly in this respect. If GUI can connect and authenticate, the .NET assembly can connect and authenticate too.

And yes, Kerberos should be seamless.

New at using Kerberos with Unix. I have a situation where I need to do SSH and SFTP from a Windows host to a Linux host that has been Kerberized. The Linux host is joined to Active Directory.

We're currently using SSH.NET but it doesn't seem to support Kerberos or GSSAPI. In doing research I see that WinSCP supports it in the client but didn't see support in the .NET assembly.

Any pointers you can provide to get this working would be appreciated. Would this somehow be seamless (similar to Windows Authentication) assuming the user running the process leverage WinSCP has access to the Linux host?

The GSSAPI authentication is enabled by default. You can turn it off using AuthGSSAPI raw site settings:
https://winscp.net/eng/docs/rawsettings#authgssapi

Is there any real problem you are facing?

I don't see any options to use GSSAPI authentication with the .NET assembly. Can that feature be added?