Temporary site unavailable setting in SPO except administrator

Question

I use ModernUI in SharePoint Online.
Is it possible to temporarily disable the system for release work, site updates, etc., except for operational administrators?
I also want to prevent users who have registered their browser's favorite sites from directly accessing the URL.
It would be great if I can display message like "Site is under maintenance".

Appreciate any ideas\Pointers. Thanks,

Answer 1

To answer your questions:

1. It is not possible to disable the system for getting release from ‎Office 365‎, it is only supported to control what release we may receive. You will have to contact Microsoft for further control on your behalf.

2. You can set a site to Read Only using PowerShell:

   Set-SPOSite -Identity <siteURL> -LockState ReadOnly

   It will display a message on top of the site that it is under maintenance and read-only, but it will disable the activities on all users who have access, including Administrators. Also it doesn’t apply to the root site collection.

   As a workaround, I would suggest you restrict user access by adjusting user permissions directly.

3. We cannot prevent users from accessing a site via the URL (or following the site) as long as they have access to it. See a related post here: How can you prevent users following your site?