Apple has released the iOS 15 developer version and you can now install it on your iPhone.
Here is a quick breakdown …
How to install iOS 15 Developer Beta:
1. Start with a full iTunes backup of your data. Fortunately, you no longer need iTunes for it: just connect iPhone to your Mac with a cable and back it up with the Finder, or alternatively, you can back up your iPhone to iCloud. This is important because you are installing beta software that is not quite final, so you may experience errors.
3. Once you’re signed in, you’ll need to register iPhone by downloading your iOS 15 beta profile. To find it, tap Downloads in the upper right corner or use the drop-down menu on the left.
4. Find the iOS 15 profile and make sure you’ve enabled the download.
5. Finally, go to Settings> General> Software Update and you should see the iOS 15 beta. Click the “Download and Install” button and you are installing the beta. After a short wait until it is installed, you will need to restart. When it restarts, it will use the beta software, and you’re done!