Conditional to not show ad on index page

How do I use this to not show on the index page and to show on all other pages in ad_above_top_breadcrumb?

How can I show content on a specific page?
<xen:if is="{$contentTemplate} == 'xyz'">

This content will show on the xyz template​

</xen:if>

 

So the opposite, to show only on the forum list page would be

Code:

<xen:if is="{$contentTemplate} = 'forum_list'">
 
</xen:if>

One step further, I want to show different ads for each code. I guess that would require an OR. I'm not quite sure how to do that properly.

 

I want to have certain ads on the forum home page, and different ad code for the topics and post pages in the ad_above_top_breadcrumb template.

 

If forum list this, or else this.

 

Perfect, thank you!