I see that TDE supports SmartCards according to https://www.trinitydesktop.org/features.php .
I also see some smart card functionality in the source code of some of the files.

What I can't find is any documentation on how to use it or set it up or any of the user space applications for it.

There are two places where I'm looking for TDE support:
Login (TDM)
Lock Screen.

I currently have TDE installed via the debian packages for it for Debian Stretch.

Can someone point me to the documentation on how to get it work in TDE?