Coveo for Sitecore 5 with Sitecore Horizon 10

When we try to use Sitecore Horizon (10.0.1) with with a solution having Coveo integration, Sitecore Horizon throws the below exception in the UI. It does not load any sites or languages in the dropdown. When we try to remove site definition with name "coveo_website", it is loading fine. As per Coveo, we should not remove this site definition as it will impact Coveo integration. 

Reached out to awesome Sitecore community in Sitecore Slack for help and Jeff (@jflh) provided a simple workaround patch configuration in the Sitecore.Demo.Platform repo. Basically we are changing the Coveo_website site definition to an item that does not exist. Horizon will not consider this site as a valid site to be editable in the editor. 

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:coveo="http://www.sitecore.net/xmlconfig/coveo/">
	<sitecore coveo:require="!disabled">
		<sites>
			<!--
				DEMO WORKAROUND
				Coveo for Sitecore and Horizon modules are incompatible by default. Horizon handles the coveo_website as a content site.
				We are applying a workaround similar to what Unicorn had done to fix the same issue: https://github.com/SitecoreUnicorn/Unicorn/issues/398
				We change the coveo_website rootPath to an item that does not exist.
			-->
			<site name="coveo_website">
				<patch:attribute name="rootPath" value="/coveo/for/sitecore/module" />
			</site>
		</sites>
	</sitecore>
</configuration>

After adding this configuration patch, Horizon started to load our sites with Coveo_website site. 

Sitecore Slack Chat: https://sitecorechat.slack.com/archives/C0CF16R9C/p1626812378104900