HMD Global/Nokia was the main reason this website came to exist. They had the most aggressive app killers preinstalled on their phones.
There were three different app killing mechanisms:
com.evenwell.powersaving.g3 on Android Pie for most Nokia phones - this one has been disabled since 8/2019 on devices running Pie or greater
com.evenwell.emm on Android Go (Oreo?) for Nokia 1 - probably still in the wild since HMD only disabled Evenwell apps for Pie or greater
DuraSpeed on Android Pie (build 00WW_3_180) for the US Nokia 3.1 (TA-1049, TA-1063) and Nokia 5.1 - this one is still in the wild
Most Nokia phones (Power saver AKA com.evenwell.powersaving.g3)
To fix this issue, please do the following:
Go to Phone settings > Apps > See all apps.
Tap on the right top corner menu > Show system.
Find Power saver app in the list, select it and Force close. It will remain stopped for a while, but will restart itself eventually.
From now on, background apps should work normally and use the standard Android battery optimizations.
Still 3rd party alarm clocks or any task scheduling of foreground tasks at a particular time won’t work. In our preliminary tests it seems that force stopping or uninstalling the Power saver app also fixes alarms and starting of foreground services, until the Power saver restarts.