Welcome to the Streamlit community, and thanks for the detailed report and links! 
You’re absolutely right—this error is due to the Debian security repository’s InRelease file being expired, which is outside your app’s code or dependency control. The error message E: Release file for http://deb.debian.org/debian-security/dists/bullseye-security/InRelease is expired confirms it’s a base image/mirror issue, not a problem with your packages.txt or requirements.txt.
This type of issue has occurred before and is typically resolved by the Streamlit Community Cloud team updating or refreshing their base containers to point to a valid, up-to-date Debian security repo. In similar past incidents, the recommended workaround was to delete and redeploy the app after the platform fix is rolled out, as rebooting alone won’t help while the base image is stale. For now, there’s nothing actionable on your end—just keep an eye on the Streamlit Community Cloud status page and the forums for updates. If you see a fix announced, delete and redeploy your app to pick up the new base image.
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