First, certbot can also be called letsencrypt on some machines. And, it is stored in various places, depending on how you set it up.

On a Devuan server, installed for ISPConfig, it is located in /opt/eff.org/certbot/venv/bin/certbot, so I will use that path for all the examples below. This is not in the path for any user, as far as I can tell, so you have to use the full path to call it.

A lot of this is taken from https://certbot.eff.org/docs/using.html, which is confusing and hard to use, but does give an exhaustive list of the commands at the bottom.

/opt/eff.org/certbot/venv/bin/certbot certificates

Sample output would be as follows. Note that you may have multiple entries, and not all entries will have multiple domains in them.

Saving debug log to /var/log/letsencrypt/letsencrypt.log
 
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Found the following certs:
  Certificate Name: mail.example.com
    Domains: mail.example.com imap.example.com smtp.example.com
    Expiry Date: 2020-10-26 12:09:56+00:00 (VALID: 37 days)
    Certificate Path: /etc/letsencrypt/live/mail.example.com/fullchain.pem
    Private Key Path: /etc/letsencrypt/live/mail.example.com/privkey.pem
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