Archiving with Teams Manager
When archiving Teams, not only is the Teams team set to the Archived state, you also get the option to set the connected SharePoint page to Read Only.
When we are in Teams Manager, we always work with the application permissions. This means that interfaces must be enabled by Microsoft (Microsoft Graph API) in order to perform certain actions/interventions. Currently there are no interfaces to set the SharePoint page to read only.
How to reach the goal
With Teams Manager, it is currently only possible to archive the Microsoft Teams team. But if you want to set the SharePoint page to read-only in the background, this can be achieved by creating an additional function, e.g. an function app, which runs once a day and triggers the SharePoint page for all archived teams and sets it to non-reading. If there are any questions you can come back to us.