Microsoft have posted an ISO of the latest Window 10 20H1 build. The ISO is available for Windows Insiders wanting to test a clean install of Windows 10 20H1. The build number is 18912 which was released to Insiders last week.
I am pretty sure this is the first ISO of 20H1 but at this stage there are not that many changes to the OS.
The ISO is available from the Windows Insider download page and here is my hands on video of the build from last week: