Apple has released the fourth iOS 13.3 developer beta for iPhone, which does not bring a host of new features to the mix and appears to add stability updates for bugs found in earlier 13.3 betas.
To update your iPhone to iOS 13.3 developer beta 1, you will need to be a registered developer. You can use the restore image for your iPhone available in the Developer portal, or install the configuration profile, then update over the air.
If you already have the profile installed on your iPhone, head over to Settings –> General –> Software Update to start installing the latest beta build, or wait until it installs automatically if “Automatic Updates” is enabled.