https://www.bleepingcomputer.com/news/microsoft/the-official-isos-for-windows-10-20h1-now-available/

Microsoft has finally released the first official ISO files of Windows 10 20H1, allowing users in the Windows Insider program or non-Insiders to clean-install the next big Windows 10 update.

Windows 10 20H1 Build 18912 ISOs are available in three variants - Insider Preview,  Insider Preview Enterprise and Insider Preview China Home.