MacRumors published a story that Apple has released the release candidate of tvOS 15.3 to registered developers.
Apple Seeds Release Candidate Version of tvOS 15.3 to Developers
Apple today seeded the release candidate version of an upcoming tvOS 15.3 update to developers for testing purposes, with the software coming one week after the second beta and over a month after the release of tvOS 15.2. Developers can download the new tvOS 15.3 beta by downloading a profile onto the Apple TV using Xcode. tvOS updates are often minor in scale, focusing on under-the-hood bug fixes and improvements rather than major outward-facing changes.
Apple Seeds Release Candidate Version of tvOS 15.3 to Developers
