Please work on it. I need an official solution for this.
Though based on various tutorial, I had tried to install Lets Encrypt SSL on multisite with subdomain and domain mapping and it ACTUALLY WORKED!! But, in the same setup, when I open domain with htpps ( like domain.com or http://domain.com ), it gives me 400 BAD REQUEST error saying:
The plain HTTP request was sent to HTTPS port.
I have written all my setup configuration in detail here: http://community.rtcamp.com/t/400-bad-request-after-installing-letsencrypt-ssl-on-wordpress-multisite-installation/8767
If you have some programming skills, please give it a look to resolve this 400 bad request error issue.