https://wccftech.com/new-windows-10-preview-is-out-blocked-for-arm-devices/

Microsoft has released Windows 10 Insider Preview Build 19587 to Insiders in the Fast ring. Today's release doesn't bring any new features and focuses on general fixes and improvements. The Windows maker also noted that it will be blocked from ARM devices due to an issue that is "causing them to receive a bugcheck."

The current builds being delivered to the Fast ring aren't tied to a particular Windows 10 version. Microsoft had said that the new features being tested will be part of future versions. It remains unclear whether that would be 20H2 or the 2021 Spring version since Microsoft may release 20H2 as service pack update similar to Windows 10 November 2019 Update.