I have set up ubuntu server on an old pc with webmin as well. I am not sure what was going on but i restarted the server and when it boots it now get this when Apache tries to start.
* Starting web server apache2
apache2: Syntax error on line 237 of /etc/apache2/apache2.conf: Could not open configuration file /etc/apache2/sites-enabled/000-default: No such file or directory
Action 'start' failed.
The Apache error log may have more information.
I have checked this file on this line and it looks like this:
# Include the virtual host configurations:
Include sites-enabled/
I have removed Apache and re installed it but not sure why it still fails.
As also answered by Qben, the issue was an invalid symlink in the sites-enabled folder. Removing the broken symlink and adding a valid one will fix the issue.