Resolve domain url to "domain/roundcube"

[joea]

This is probably a simple fix for those experienced, but . . .

I'm trying to make my domain point to roundcube.   That is, so that "https://main-domain.com" would  got to "https://main-domain.com/roundcube"

I have a pretty vanilla setup on OpenSuse 15.4 with a virtual server for roundcube (v 1.5.3).   That virtual server contains several "alias" statements as I have a couple of domain names.

I've attempted to use the Redirect directive (?) in several  places (Redirect "/" "/roundcube") in various locations, but only succeed in changing the "forbidden" message to one that says 'attempting to redirect in a way that will never complete', so clearly my hacking skills are stale.

This section of /etc/apache2/conf.d/roundcubemail.conf may help describe what exists:

<VirtualHost *:443>
     SSLEngine ON
     ServerName wmail.main-domain.com
     ServerAlias webmail.main-domain.com
     ServerAlias wmail.not-main-domain.com
     ServerAlias wmail.1not-main-domain.com
     DocumentRoot /srv/www/roundcubemail
 . . .#lots more stuff
</VirtualHost>

[joea]

Simple solution.  Forced to re-read the installation section the solution was described. 

"When running Roundcube at root of a virtual host, it's recommended to set the document root of that virtual host to the public_html directory of your Roundcube installation - but only after installation is complete, because the installer/ directory is unavailable otherwise."

Remarkable that not even RTFM was suggested.