Welcome to the Streamlit community, and thanks for sharing your question and details! 
This is a known limitation: when you change your GitHub username, Streamlit Community Cloud may not automatically update your displayed username or profile mapping. The platform identifies apps and profiles by the original GitHub coordinates, so even after a successful username change, your public profile and “Created by” badges can still show the old username. Logging out/in or clearing cache usually won’t fix this.
To resolve this, a Streamlit staff member needs to manually update your username in their backend database. You’ve already provided the necessary details (old/new GitHub usernames and email), which is perfect. For reference, this process and its limitations are discussed in the official docs and forum threads—community members have had success after staff intervention. If you haven’t already, you can also open a support ticket or reply to this thread for staff to pick up your request. Community members, feel free to jump in if you’ve had similar experiences or tips!
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