Restrict content from M365 Copilot
If you are implementing Microsoft 365 Copilot in your organization, you may decide to enable the option to Restrict content from Microsoft 365 Copilot within the Settings for a site in the SharePoint Admin Center.
As described in the Info for this option, doing this will generally prevent the content in this site from being discoverable from elsewhere in the tenant.
Microsoft's documentation recommends enabling this option only for sites with the highest risk of oversharing. They also suggest that this feature may be used as an initial step to prevent discoverability while getting the site's permissions in order - which is the longer-term best practice. If discoverability is simply disabled with this restriction setting, then you will reduce the effectiveness of having Copilot to begin with.
We recommend using our DeliverPoint permission reporting and management tool to see where oversharing has occurred, and to have site owners and/or IT staff report on and manage peoples' access to content. View this webinar recording to learn how: SharePoint Permissions Management Made Easy with DeliverPoint.
Effects on the Lightning Conductor
Because this setting restricts content from appearing in org-wide search, if you have a Lightning Conductor that is using the Search rollup option to display items from a site that's been restricted, then new content will no longer appear in the Lightning Conductor. If the site must remain restricted, then you may need to switch to using the Object Model rollup option, though that will likely impact performance.
When using the Object Model rollup option, the Lightning Conductor uses SharePoint Search to populate the Treeview of sites from which to display content. A restricted site will no longer be available in the treeview, although you will be able to add a site collection filter to find it.
Another potential side effect occurs if you have not deployed the Lightning Conductor to all sites, but rather you've added it only to specific sites. In that scenario, on a restricted site, it will no longer be available in the web part toolbox to add to a page.
Effects on DeliverPoint
DeliverPoint uses SharePoint Search to populate its Treeview (the leftmost panel), so it will no longer display restricted sites. To report on and manage permissions on these sites, you will need to navigate to the site itself.