Is it just Webmin that this is occurring with, or does the same issue also occur when you try to connect to https at all?

Also, just to be sure, you're aware that by default TurnKey ships with "self signed" SSL certificates. Whilst they aren't explicitly a security issue (if you are expecting self signed certs), because anyone can make them and could theoretically pretend to be anyone, they will cause a security error in any browser. You will need to click through that error message before you can access the page.

Assuming that that isn't the issue, AFAIK usually a "SSL connection reset" error message is because the browser and the server can't find a mutually compatible SSL/TLS version to use. In v16.x we disabled downgrading to anything below TLS v1.2, so if you are trying to connect from a device that doesn't support at least TLS v1.2, then perhaps that's the issue?

Having said that, unless you are using a really old unsupported OS or an old Android device or similar, that also seems somewhat unlikely.

Some things that I would recommend to test are (in no particular order):

• clear browser cache and cookies
• and/or try via a new private/incognito window
• and/or try a different browser
• and/or try from a different computer/device

If you continue to have issues, please share the info from the Apache logs. Hopefully that might give some further info. You'll find the Apache logs in /var/logs/apache2 (most likely error.log will be the one that has the relevant info).