In order to install Let's Encrypt SSL certificate, please do the following:
1) Connect with SSH to your SMSEagle
2) Run the following command (depending on your device type)
a) for NXS-97xx Rev1 (device MAC starts with 78:a7:14:54)
Guidelines how to use can be found here: https://github.com/Neilpang/acme.sh
b) for NXS-97xx Rev2 (device MAC starts with 78:a7:14:55)
c) for NXS-97xx Rev3 (device MAC starts with 78:a7:14:56 or 78:a7:14:64 or 78:a7:14:65)
and proceed with on-screen commands to obtain a SSL certificate.