You will find the release notes for Windows IoT 4.03.100 as a text file next to the installation programs on our download server and on our Knowledge Base.
Added support for UEFI Secure Boot. The boot mode is displayed in the IGEL Device Information tool (Hardware tab); see here.
In the Rescue Shell you can now overwrite the network information. They are then valid for the current session; see LAN Interface.
FTP is available as a new snapshot protocol; see Snapshots.
The display configuration tool has been redesigned; see Display.
The option Enable Single Sign-on through ICA file (Sessions > Citrix > ICA Global > Options) does have no effect anymore; as of now, this option can be configured under Sessions > Citrix > Self-Service Plug-In > Logon; see Logon.