I have a Highlighted Content web part on a hub site that shows news intended for ALL employees (intranet) with content being rolled up from various functional area sites connected to said hub. I am filtering by managed properties, which works fine. The issue I have is that not all of the content in the functional area site pages is intended for ALL employees. I found a way, I think, HERE, to use Flow and REST Api to set item level permissions to "Everyone except external users" so that only those items with the managed property of ALL are visible to all employees. Other items in Site Pages would stay set to Functional Area permissions. It looks as if I will need the GroupID. Does anyone know what that might be for "Everyone except external users". Or a better way to accomplish my goal? Much help is appreciated.
based on the additional points shared in the comments section, I feel you can look at the following model to achieve the need:
Create a sub-site, say 'Private', under 'Executive Site', which should be accessible only by 'Executives'. You can have a new group created only for 'Executives' and break inheritance on the sub site to provide permission only to that group.
Now, have 'Everyone except external users' group added as 'viewer' in your top level 'Executive Site'.
News created in 'Executive Site' and the 'Private' sub-site, both would roll up to the Hub. There is no way you can stop the roll up if you are using 'News' pages. 'Everyone except external users' (not members from 'Executives' group), will see news items published in the 'Executive Site', but they won't be able to see any news from the 'Private' sub-site. News from 'Private' sub-site should be visible only to the members from 'Executive' group.
Let me know if this model will match your need.
Using managed property to filter News will work visually, but it will not necessarily restrict unwanted user-groups from viewing the content. They can always grab the direct link of the page to browse it. So, there should be restrictions through permission.
Just wanted to add that, SharePoint news audience targeting feature is in development which would give you more options over your particular issue.
Please check Microsoft Roadmap for SharePoint Online.