Like to live on the edge, or want to see if the next iOS release fixes some of the bugs you're suffering with right now? Why not take the current iOS public beta for a spin?
It's quite straightforward, and you can roll back at any time.
The next thing you need to do is visit Apple's Beta Program home page in Safari on the iPhone you want to switch to the beta and either sign up or sign in.
Betas are available here for iOS, iPadOS, macOS, tvOS, and watchOS.
From here you can enroll the device and then download a profile to your iPhone. Once that's in (it cakes seconds), head over to Settings, tap the profile and follow the onscreen instructions to install the profile.
Once that's done, go to Settings > General > Software Update to download the beta. It's a full download so will take some time.
Note: Installing a public beta does not affect your warranty.
To leave the beta, you will need to unenroll your device and then carry out a software update to download the latest release of iOS.