https://wccftech.com/download-ios-13-gm-for-iphone/

You can now download iOS 13 GM (Gold Master) for iPhone right away if you are a registered developer.

Today’s a great day if you are an Apple fan. Apple has just released for download iOS 13 GM. The Gold Master candidate is not available for iPad users. The Gold Master is essentially the potential candidate for the final build. If no bugs or hiccups are found then the GM will be released as-is to the public in a few days time. However, if something grave is found by Apple, then the company will be forced to release the second GM build or just push out a slightly updated version to the public. In any case, you can now download iOS 13 GM if you are a registered developer with Apple.