In Android 8.1 Oreo as well as Android 9 Pie, if you want to install an app from outside the Google Play Store, you have to enable the “Install unknown apps” permission for any applications you’ll be using to install APKs. Once you’ve enabled that permission, it stays enabled until you disable it manually.
However, this does not appear to be the case in the first two betas of Android Q. In the most recent beta, you have to enable the “Install unknown apps” permission each and every time you want to install an APK.
As you can see, when I tried to install the Pulse SMS APK from Google Drive, Android Q asked me for permission to install the unknown software. I toggled that permission on and then the app installed as normal.
However, when I tried to install the same Pulse SMS APK from the same source (Google Drive), Android Q asked me again to enable the permission.
In other words, if you install a lot of APKs from outside the Play Store, you’re going to have to do a lot of tapping within Android Q.
Of course, this is just a beta of Android Q and this could be a bug. It’s possible that the stable version of the OS won’t behave this way, and instead work more like current versions of Android.
That being said, this does seem like the kind of “feature” that would line up with Google’s emphasis on security and privacy with Android Q. It’s certainly possible that this feature will make it to the stable launch.