layout.friendly.url.page.not.found property is broken.
Steps to reproduce:
0. Set the below config in <LIFERAY_HOME>/osgi/config/com.liferay.release.feature.flag.web.internal.configuration.ReleaseFeatureFlagConfiguration.config to allow private pages on master.
1. Start up the portal and login with admin
2. Create a public page "login" and put the login portlet on it
3. Create a public page "page-404" with some web content saying page-404
4. Create a private page "dashboard" with some web content saying dashboard
5. Add the following properties and restart the portal:
6. Add a valid virtual host name to hosts file, e.g.: test.liferay
7. Go to site settings > Site URL > and set the private pages virtual host to "test.liferay"
8. Go to System Settings > Login and check Prompt Enabled
9. Sign out
10. Go to test.liferay
Actual result: gets redirected to page-404
Expected result: get redirected to the login page
If you remove the layout.friendly.url.page.not.found property, then you get redirected to the login page again. I am not sure which is the right behavior, but there is a change for some reason.