Microsoft released the official ISO image file of the Windows 10 20H1 preview build 19041. If you are a Windows Insider, you can now download the ISO file to perform clean installation of the build which was released to Fast Ring in December 2019.
Microsoft is expected to release the final build of Windows 10 20H1 in Spring 2020. But, before that if you want to grab this build, you need to register as Windows Insider.