I use caddy and it does everything for me, but my limited understanding is that the dns entry for which the certs are requested must point to the ip address at which caddy is listening. So if I have a DNS entry like internal.domain.com which resolves to 10.0.0.123 and caddy is listening on that address I can get a http connection, but not an https connection, because letsencrypt can’t verify that 10.0.0.123 is actually under my control.