Pretty sure if you can find some official advise that these are not recommended at the top of the stairs (NHS or something) then your Landlord can't make you use them...
Noma flat step from smyths or safety first flat step
I have one on my kitchen door and a few times Iv knocked it and it comes off. Wouldn’t find one safe at top of the stairs.
I’ve got a noma one from Smyths. Fitted correctly they don’t budge at all
We have one on our kitchen to keep her away from the cat litter and food bowls and it comes off a lot so I wouldn’t want it at the top of stairs! X
I don’t think they’re recommended at the top of the stairs unless they’re fixed into the wall. You may be best off just putting them in the bedroom doorways and not letting them out onto the landing alone. Think that’s what we’ll be doing anyway
I got the cuggl stairgate from Argos at the top of the stairs, it’s pressure fit and swings closed behind you and it’s really sturdy