nixCraft published a guide about securing Lighttpd with Let’s Encrypt TLS/SSL certificate on Debian or Ubuntu.
How to secure Lighttpd with Let's Encrypt TLS on Debian/Ubuntu
Explains how to install, set up and secure Lighttpd web server with Let's Encrypt free TLS/SSL certificate on a Debian or Ubuntu Linux system.
How to secure Lighttpd with Let's Encrypt TLS on Debian/Ubuntu - nixCraft