One day after releasing the first iOS 13.1 and iPadOS 13.1 betas, Apple has provided participants of its beta program with a new seventh build of macOS 10.15 Catalina for testing.
The new build can be dowloaded alongside others in the test program from the Apple Developer Center by participants in the scheme, or as a software update for Macs already enrolled in the beta program. Those taking part in the public Apple Beta Software Program will typically gain access to its own build very shortly after the developer variant is distributed.
Even this close to a release, both AppleInsider, and Apple itself, strongly suggest users avoid installing the betas on to "mission-critical" or primary devices, as there is a very small possibility of data loss, or other issues. Instead, testers should install betas onto secondary or non-essential devices, and to ensure there are sufficient backups of important data before updating.