I've never had a car where you could disable the passenger-side airbag. We did have a car like that in the 90s, but it didn't come that way from the factory: my mother had a mostly-irrational fear of them (she was on the shorter side, but not so short that it could actually be a danger for her if it deployed), so we somehow got an aftermarket mod that let her disable it when she was riding in that seat.
Of course, she drove that car often enough too; not sure why she felt having the driver-side airbag enabled all the time was safe, but not the passenger-side airbag. (Mom was... often inconsistent with how she reacted to her fears.)
Some newer vehicles will automatically disable the front passenger airbag if there is nothing in the seat or if there is weight in the seat but less weight than a typical adult.
Pickup trucks without a backseat have long had the ability to manually disable the passenger airbag.
It's literally the law to have that feature for decade(s) now, whats going on in this conversation?
Check the area near the hinge on the front passanger-side door, there should be a labelled thing you can turn to disable it. (using a key or screwdriver, similar to the rear childlocks)
It might be due to me being in Europe, but every car I've ever seen with an airbag for that seat has had it along with a sticker warning about it in the sunvisor area.