With iOS 16.4, which Apple released earlier this year, they made it easier to join the beta program for future iOS updates.
Instead of having to install a configuration profile from Apple’s website and restart your device, you can now simply choose to receive beta updates in settings. This change is now also coming to macOS and watchOS with the upcoming updates that are currently in beta.
We will have to wait for macOS Ventura 13.4 and watchOS 9.5 to be released in order to access beta versions more smoothly.