You might also want to take a look at Caddyserver or Trafik container if it’s just static files (e.g. you don’t need Wordpress etc for content mgmt). Both have ACME built-in with Let’s Encrypt support in the container that largely automatic. See http://forum.mikrotik.com/t/container-traefik-on-rb5009/165849/6 for traefik. I don’t have writeup for caddyserver, but works on RouterOS container.