In addition to the first public beta of macOS Catalina, Apple has seeded the first public betas of iPadOS, iOS 13, and tvOS, all of which were previewed at last month’s Worldwide Developer Conference.
The public betas are available on Apple's Beta Software Program website. Just remember that beta software, so proceed with care. Apple does public betas in order to increase the size of the pool of testers. The tech giant recommends keeping back-ups of your files before installing a public beta.