A few more steps...

Delete the downloaded update package

Please make sure you already deleted the downloaded update package in Setting > General > iPhone Storage (or iPad Storage).

If you don't see any downloaded update package of iOS or iPadOS appear here, move on to the next step.

Install profile

From your iOS device, go to BetaProfiles.com to download the configuration profile. Your iOS device will notify you when the profile has been downloaded. Open Settings, tap the profile and follow the onscreen instructions to allow installation.

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Remember to restart

Don't forget to restart your device after installing the profile so any changes can be applied.