MacRumors published a story that Apple has released the second betas of iOS 15.3 and iPadOS 15.3 to registered developers.
Apple Seeds Second Betas of iOS 15.3 and iPadOS 15.3 to Developers
Apple today seeded the second betas of upcoming iOS 15.3 and iPadOS 15.3 updates to developers for testing purposes, with the new software coming three weeks after the launch of the first betas and a month after the launch of iOS 15.2 and iPadOS 15.2.
Apple Seeds Second Betas of iOS 15.3 and iPadOS 15.3 to Developers
iOS and iPadOS 15.3 can be downloaded through the Apple Developer Center or over the air after the proper profile has been installed on an iPhone or an iPad.