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