https://wccftech.com/how-to/how-to-remove-ios-15-beta-profile-from-iphone-before-installing-official-build/

If you are running the beta build of iOS 15 on your iPhone, it would be vital for you to remove the profile before you proceed to install the official build. Apple has just released iOS 15 for all compatible iPhones with a boatload of new features and under the hood improvements. If you are not familiar, we will let you know how you can remove the iOS 15 beta profile from your iPhone in order to install the official build.

Apple seeded the first beta of iOS 15 in June to developers and public beta testers. Now, the company is finally releasing it for the general public. If you are not a developer, you can install iOS 15 on your iPhone without any problem. However, if you are running the developer beta profile on your iPhone, you should remove it before you install the official iOS 15 build. This is how you can do it.