You can upgrade from Windows 10 LTSC to Windows 10 semi-annual channel, provided that you upgrade to the same or a newer build version.

This was corrected in the Windows 10 LTSC 2016 release, which will now only allow data-only and clean install options. Note: Windows 10 LTSC 2015 did not block this upgrade path. In-place upgrade from Windows 7, Windows 8.1, or Windows 10 semi-annual channel to Windows 10 LTSC is not supported. See the Windows lifecycle fact sheet for availability and service information. Work with your account representative if your current version of Windows is out of support. Windows 10 version upgrade: You can directly upgrade any semi-annual channel version of Windows 10 to a newer, supported semi-annual channel version of Windows 10, even if it involves skipping versions. Edition downgrade is also supported for some paths, but please note that applications and settings are not maintained when the Windows edition is downgraded. These methods require that you input a license or product key for the new Windows edition prior to starting the upgrade process. Methods and supported paths are described on this page to change the edition of Windows. If you are also migrating to a different edition of Windows, see Windows 10 edition upgrade. Migrating from one edition of Windows 10 to a different edition of the same release is also supported. This includes upgrading from one release of Windows 10 to later release of Windows 10. You can upgrade to Windows 10 from Windows 7 or a later operating system. This topic provides a summary of available upgrade paths to Windows 10.

Windows 10 1511 to 1703