I recommend avoid deactivating the Web Pages itself, there are a few Site Settings that can help you with that
in regards disable login, I wouldn't really recommend that, you might need to clear the cache from time to time in your Portal to reflect the most recent configuration, I am giving two options to disable login below here
Disable Search:
set the Site Settings "Search/Enabled" to false
Disable Login (personally I don't recommend):
set below site settings to false, you will need to Restart the portal via Admin Center to reflect, as some of this are loaded when the website starts in Azure/server level: https://docs.microsoft.com/en-us/powerapps/maker/portals/admin/admin-overview
- Authentication/Registration/Enabled
- Authentication/Registration/AzureADLoginEnabled
- Authentication/Registration/ExternalLoginEnabled
- Authentication/Registration/InvitationEnabled
- Authentication/Registration/LocalLoginEnabled
Even by deactivating the above, the SignIn link will still be present on the menu, and you need to hide it via JS, which comes to my recommended approach
Disable Login (recommended):
Leave at least one login type enabled for clearing cache purposes, and hide the sign in via JS
- Open the Web Template Header, and at the bottom there is some JavaScript code, within the window.onload function add the following code:
$('a[href^="/SignIn"]').hide();

- The above will hide the SignIn link, but you might notice that there is a small delay, and the user will still know that the SignIn exists, so I recommend changing the SignIn text to a simple "-" or "."
- Create a Content Snippet called "links/login" with the text

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