You should have used the `--deploy-hook` on certbot. I use this to copy the cert to Synology NAS and trigger a reload of the cert on the NAS.

BTW: The easiest way to run certbot in a container is to mount a renew script (some shell script as simple as `certbot renew`) to /etc/periodic/daily/renew, then change the container's entrypoint to `crond -d6 -f`.