All logs configured are listed correctly when opening System Logs RS but when I try to view any of the logs the it fails – the red line at the top of the viewport (the loading indicator) just keep on.
The File Manager fails in the same way. Trying to edit or view any file fails, even the smallest ones.
A workaround could be to download the log file on your desktop and work it from there. What could also help is to filter the log file with ‘Only show lines with text’ feature.
Check the miniserv.error log, and also open the Web Developer console and watch for relevant errors. It’s possible there’s something has changed that is a problem for the quite old Perl in Ubuntu 16.04.
Note that Webmin 2.200 is not the current version, and is not a version we ever pushed to the Virtualmin repos (because bugs were discovered).
Are you using Cloudflare proxy with a lot of security features enabled? If so, do you experience the same issue when connecting directly to your server’s actual IP address, like IP:10000?