Yes! I do with NGINX using SNI (to server multiple ssl certs from the same IP) and using Proxy Protocol on the ELB to send the requests to NGINX.

What you need to do is enable the proxy protocol on the ELB and then point to NGINX. http://docs.aws.amazon.com/elasticloadbalancing/latest/class...

You need to also enable the proxy_protocol in nginx.

  server {
    listen    443 ssl proxy_protocol;
    ...
  }

I'll write something up and share it. But hopefully this will help you in the short term.

That would be very kind, thank you. I'm not the particular dev who has been doing the research, but I might read his notes later to catch up to what he perceived as the pitfalls of using ELB with LetsEncrypt.

You need to use SAN certificates to do this (Which LE will do). You just need to be comfortable with having every domain registered appearing on the certificate.