Over the last month letsencrypt client takes almost one hour to create a new certificate (I think I have the same behavior for renewal).
I run this command on my server : ./letsencypt-auto certonly --agree-tos --standalone -d summer-beach-party.fr
With the debug flag I noticed that time is spent at these points : “Starting new HTTPS conenction”.
My server is hosted at online.net. It is configured to run over ipv4 and ipv6.
If you need more information I can provide them.