I work at Univention in Germany and wanted to add Univention Corporate Server (UCS) to the list of OS (UCS is an enterprise Linux distro based on Debian).
in UCS 4.1, apache Web servers, and Mail servers (dovecot, postfix) on top of UCS can use a “small Let’s Encrypt client” for UCS to generate and work with certificates. The script uses UCR variables (UCS configuration variables) to specify which services and on which domains the certificate is valid. And by default, a cron task will try to renew the certificate every month.
The UCS forum mentions that the script is being adapted for UCS 4.2.
Some people in the (German) forum have reported other clients like Certbot or Dehydrated to have worked for them on UCS too.