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Real certificates (issued via the production server) are truly valid Secure, and will show as Issued by: Let's Encrypt Authority X3
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For more information on the differences between staging and production on LetsEncrypt, see https://letsencrypt.org/docs/rate-limits/
Migrating from Staging to Production
If you've made it this far using staging, then you are probably ready to start issuing real certificates - simply change https://acme-staging-v02.api.letsencrypt.org/directory above to https://acme-v02.api.letsencrypt.org/directory
You may need to manually delete your old secret to get cert-manager to create a new one with the real TLS certificate and, once it has been recreated, touch your ingress rule.
Deleting secret out from under the Ingress Controller puts it into a bad state, but this is corrected when the Ingres Controller detects a change to the rule and reloads it.