I understand your impatience but we will release it when it's ready. Currently, we fix bugs to stabilize the code for the 3.1 release. You can get the code at any time from git.ispconfig.org and install it on your server, just ensure to use the stable-3.1 branch.
@till Is there approximate time ? (Days, Weeks, ...) As an ISPConfig developer, Is the code here (https://github.com/alexalouit/ISPConfig-letsencrypt) trustable ? Is the developer (of the previous code) a member of ISPConfig team ? Due to your suggestion I prefer to wait for the release because I want to use the new feature on a production server and the unfixed version will not be good for this specially the current/working version is stable.
A beta will be released the next days. The final probably end of Mai or in June. I haven't used or checked this code. The official 3.1 code is based on it if I remember correctly but we also changed things so not sure if an update to 3.1 will work without breaking your SSL certs when you use it.
