When SP 2010 sites are migrated using STS3 Modern Template without Office365 group, the Site Permissions pane at the root level is not working as expected. We are unable to add users or groups on the default SharePoint Groups. Not showing the existing users or groups that were migrated from SP2010 site. the site permissions pane will be missing the three Associated Groups .
Associated Default Groups in Site permissions are not retained after a migration to Modern pages in SharePoint Online
the groups are migrated, they are just no longer the 'Associated Default Groups'.
