Windows Autopilot supports Windows 10 Enterprise 2019 LTSC which means it should support IoT Enterprise 2019 LTSC since they share the same media: -us/windows/deployment/windows-autopilot/windows-autopilot-requirements. If you run into problems using Windows Autopilot with LTSC 2019, we can help to connect you with the right team for follow up.
Thanks for your awesome questions.
Cheers,