Android 8.0 in 2017 made it harder for users to install APKs downloaded from sources outside the Play Store. A new behavior in Android Q takes this a step further by disabling that permission after every install.
On Oreo and Pie today, users are presented with the following prompt the first time they want to install a downloaded APK. They can “Cancel” or tap “Settings” and be taken directly into the App Info page to “Allow from this source.”
For your security, your phone is not allowed to install unknown apps from this source.
On those stable operating systems, that permission is set in perpetuity. However, in both Android Q Beta 1 and Beta 2, “Allow from this source” disables itself following an APK install. After an attempt from Google Chrome, Drive, etc. is complete, that toggle is automatically disabled by the system.
Users are re-shown the “For your security” prompt with shortcut into App Info when they want to install another app. Meanwhile, if users head into settings and enable the permission, but do not install an app, it will remain on until the next installation completes.
While this could get annoying for power users, in the grand scheme it is safer for casual ones by slowing down the process and requiring them to consciously think about the install. It will also show the “Your phone and personal data are more vulnerable to attack by unknown apps” warning every time they visit the page to switch on the toggle.
Assuming this new behavior is not just a bug, Google should likely redesign the prompt to be more explicit about the change. Otherwise, it looks like a fault on the system for not remembering an end user’s set preference.