Except for a small number of apps, I've disabled "Background Data" for almost all apps (as well as battery background usage). The description under "Background Data" states "Enable usage of mobile data in the background" (which suggests it's only preventing background data over mobile but not over wifi). I use NextDNS and noticed on NextDNS log, that even after restart, before even running any app, many apps are using the internet in the background over wifi.
Is there any way to prevent apps from using ANY internet in the background (mobile or wifi) unless I open them?