For a Hippo 10.2.1 project with no manual overrides we are encountering a problem saving hst:pages configuration. This problem occurs when creating a new url matcher without interacting with the hst:pages selector.
Go to cms
Open channel manager and any site, click edit and open the url- and navi.. menu.
select new url matcher.
Enter any url name
choose any content document.
Do not interact with the page configuration but notice it mentions your fist hst:pages node (in our case hst:pages/default),
return to the site perspective of the channel manager.
Save & quit and publish the changes.
Go to the console
find your new sitemap item
notice the lack of componentconfiguration id, meaning the hst:pages (hst:pages/default) is not saved.