I did used virtualmin before and i could request letsencrypt ssl certificate for a domain, and can also click on the "Copy to Webmin" button to use that certificate for logging in webmin.
However, 2-3 days ago i did a clean install of the newest virtualmin, on ubuntu 14.04. I was able to request lets encrypt ssl for a domain, but cannot "Copy to webmin". It doesn't say any error, but the certificate was not used, i still have to make an exception in browsers. I tried firefox, chrome, IE, all of them have problem, even after i clear all caches and cookies.
I tried "Copy to usermin" and see it works . i can open mydomain.com:20000 normally in all browsers with lets encrypt simbol in the address bar.
So i guess there is a bug in the new virtualmin version. I tried installed in another VPS provider and see the same problem.
Could anyone try and confirm?