Link: https://www.linode.com/docs/guides/deploy-a-flask-application-with-dokku/
Issue
This page appears to be slightly outdated; at least for Debian 11 that I tried it on. When I follow the instructions I get the following error message:
W: GPG error: https://packagecloud.io/dokku/dokku/debian stretch InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY FB2B6AA421CD193F
Suggested Fix
Update article to reflect the latest version. Also investigate the issue with the gpg key and add additional notes about it in the troubleshoot section.