How to force a smartphone to do update? How come two Nokia 9 phones have the same model, phone service provider and location, but one of them insists there were no updates (neither security nor Android itself which should be 10, not 9, by now) after 2019?
You can see Nokia had many security updates after 2019.
Neither taking out the sim card nor a factory reset helped with this.
P.S.
This phone is Android One, so it's even more concerning.
Neither taking out the sim card nor a factory reset helped 

The following was suggested by Nokia itself. But turns out they didn't think to suggest doing both at the same time.
Although it can be far easier - just turn off Mobile Data, then check for updates. If it's not enough, also restart the phone while keeping Mobile Data off. Suddenly you get updates.
I'd chalk it off as a bug that lets the phone provider save bandwidth for itself even though you actually use WiFi for updates.