Ever since Android 8.0, the "Allow from unknown source" option has been removed.
Now you have to enable "Install unknown apps" with a specific already-installed app.
But what if you need to reinstall your firmware and you need "unknown source" enabled while the phone is in flashmode?? There is no solution.
I already have 8.0 installed so I no longer have the "unknown source" box. I have individual apps to enable "install unknown apps". However, none of those apply to install while in flashmode. I tried enabled "Install unknown apps" on every single app. It still doesn't apply to the phone while in flashmode.
I have already tried Sony PC Companion, but it does not resolve the problem.
(https://support.sonymobile.com/global-en/xperiaxz1/userguide/restarting-resetting-and-repairing/)
So my next solution is to use Flashtool (https://droidfeats.com/sony-official-firmware-download-android-8-0-for-xperia-devices/#Preparation_S...)
However, Flashtool requires you to have USB Debugging and Unknown Source enabled in order to flash via flashmode. USB Debugging is enabled. Unknown Source can not be enabled.
There are apps that allow you to enable "Unknown Source".. but those require root. And in order to gain root, you still need to use Flashtool. So that's not an option either.
Member Sarah21 asked this same question a month ago (/t5/Xperia-XZ-Premium/Unknown-sources-option-is-missing/m-p/1340366)
Sony was unable to provide a solution.
So at this point, I can not flash my official firmware since I can't even meet the the prerequisite of having "Unknown Source" enabled while in flashmode.
What is the solution to allowing "unknown source" for anything outside of "Settings > Apps & notifications > Advanced > Special access > Install unknown apps"?
What is the solution to allowing "unknown source" for use during flashmode?
