@Anke I have been following this topic for a long time and I have faced exactly all these problems. I've tried all the proposals, I installed several of the extensions mentioned here and some more I found on the internet... but NOTHING worked on my Samsung. After 4 minutes and little the screen darkened slightly... and when it was 5 minutes it enters into "Doze Mode", with no chances of continuation.
But after many tests I found a solution. I just didn't expect this topic to be resurrected after so long.
The solution was to uninstall all tested extensions, just keep 'taifunbatteryoptimization1' » RequestIgnore, and simply regularly use 'Notifier'» ShowAlert » 'Notice', with a blank text string. For this not to be displayed on the screen, on the properties of Notifier the 'Appearance' must be with BackgroundColor and TextColor set to 'None'.
In the first instance where the Timer is triggered, a variable holds the 'Start' and already program the 'Alive Notification' 4 minutes later. This can be parametrized for another lapses...
Once this 'Momentum' comes, the simple Notifier call with blank string has the ability to keep the screen Alive! At this point, just schedule the next Notification for 4 minutes later... and then the device does not enter in Doze Mode and the screen can be active until the battery is over.
I am happy that this topic has been reactivated so I can share this solution.
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