Here is my settings; http://prntscr.com/9ptrqc with the error.
I am able to use the SSL certs form my main website fine but i can’t get them to work with Webmin… I want to link them like this so i can auto-renew the certs when needed and they will just be loaded.
The certificate served for that site is valid. The issue seems to be that Webmin is including some JavaScript file via HTTP instead of HTTPS. I’m not familiar enough with Webmin to know what could be causing this, but sometimes it’s due to some kind of base URL (if Webmin has something like that) being set to http:// instead of https://. I would also take a look at other modules you have installed. Your Chrome’s DevTools (accessible via right-click > Inspect) will probably contain more information about which script Webmin is trying to include via http.
The obsolete cipher suite warning can probably be fixed by switching to “Only strong ciphers with perfect forward secrecy” (unless you have to support outdated browsers for some reason).
This is what I got differently than in your setup:
SSL protocol versions to reject SSLv2 and SSLv3
Allowed SSL ciphers Only strong ciphers with perfect forward secrecy
Didn’t provide the Additional certificate files this SSL setup is working for me.
**NOTE:**See “Let’s Encrypt” in your SSL Encryption of Webmin configuration provide the dir and client /Path/To/LetsEncrypt/letsencrypt-auto and other settings you want to request a (re)new certificate
Change log: Version 1.780 (30th December 2015)