There isn't and such a list won't be made in the future too. Let's Encrypt keeps the right to change the IP addresses used for authentication at will and won't release lists of it for security reasons.
To me it sounds a bit like "security by obscurity", but that's the current Let's Encrypt policy as far as I know.
If the http-01 or tls-sni-01 challenges can't be used because of such strict limititations, you can always look into the dns-01 challenge.