I asked support why on Android 9 my task switcher doesn't store many apps:
I just updated my phone from Android 8.1 to the latest build of Android 9 for the Nokia 8.
task switcher in Android 9 does not store as many apps as in Android
8.1. On Android 8.1 I could keep 5-6 apps in the task switcher view
without problem and if I opened a lot of apps it would gradually reduce
this to 5-6 again. This was acceptable as it normally kept my most
frequently used apps available. However, Android 9 is much more
aggressive at removing apps from the switcher view - too aggressive, it
always reduces the amount of apps shown to just 3, which is not
sufficient. It is actually inconvenient to use the task switcher,
because I open it and see that the app I want isn't there and I have to
go to the launcher and reload it - it takes at least twice as many
actions and more than twice the time than on Oreo 8.1. The really
frustrating thing is that I know the apps are still running in the
background because they give me notifications! Please tell me how to
allow the task switcher to keep more apps available, which setting do I
need to change?
Another problem is that I
often get a case where the task switcher doesn't show me
previews of the apps, only blanks. I can't find a pattern for this
behaviour but I would like to stop it happening. Is there a setting
which controls this?
And this is the reply
You can disable adaptive battery and some other power
saving features in order to see if you can improve the situation with
the available background application number.
Please go to: Settings -> Apps&Notifications -
show all apps -> three dots -> Show system -> Battery
protection -> Disable.
What?! Really?! After stories of exploding batteries etc why on earth would I want to disable the protection for my battery?!
As it turns out, I don't actually have a system app on my phone with that name. After searching the forum here I know exactly the one that they mean, it's the Evenwell one which many people are suggesting can be disabled to improve retention of background tasks and also improve battery life.
Still, should support really be suggesting that people do this?