Certbot SSL error "Unrecognized challenges: tls-sni"

When I am try8ing to create an SSL certificate on port 443, I get the following error:

certbot: error: argument --preferred-challenges: Unrecognized challenges: tls-sni

Port 80 is already in use, so I am following the instructions of using “–preferred-challenges tls-sni” but it does not seem to be working.

Not sure if I am missing anything. Following this tutorial:

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October 6, 2023


The error you’re encountering is due to the deprecation of the tls-sni challenge by Let’s Encrypt. This challenge method is no longer supported because of some identified vulnerabilities.

As for PORT 80, what is listening on that port? You can check by running:

netstat -tulpen | grep 80

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