Under Nokia it says that its Android One phones are aggressively killing apps as well. Isn't Android One a phone with vanilla Android install without vendor crap by definition?

I'm happy that I'm using LineageOS. My phone is turning 7 years old, and it's running Android 9, and I've no reason to switch so far.

They are (I own a Nokia), but you can go into Battery Optimization in the settings and tell it to not optimize an application. That, I find, tends to leave it alone much better.

It is the only way I can get my K-9 mail app to stay alive to sync my email.