Remember all of the OS betas that went out from Apple to developers on Tuesday? They all went out to Apple’s public testers on Wednesday. Apple Insider says Apple made the second betas of iOS and iPadOS 15.4, macOS 12.3, tvOS 15.4, and watchOS 8.5 available to members of the public beta program.
Not to be taken internally and not to be installed on machines on which you rely. Apple Insider says both it and Apple “strongly recommend users don't install the betas on to ‘mission-critical’ or primary devices…” While they probably won’t brick your machine, they are betas so you never can say for sure. That said, if you’ve got a test device laying around or just like living on the edge, you can get more info on Apple’s public beta program at beta.apple.com.