I have one that is 20 years old and two that are not even 5 years old, but they all have a rubber knob keyboard. My question now is: were there models that were delivered with a built-in mechanical keyboard?
There are very, very few mechanical keyboards in laptops, but semi-mechanical switches like Apple's Scissor switches are more common.
It also doesn't make much sense, since the hub for laptop keyboards is usually It is less than 2mm and there's always bottom out, haptic feedback can easily be achieved even without a classic mechanical switch and acoustic feedback is not wanted with mobile devices, otherwise it would be harder to use it in work or other quiet environments.
I don't know of an IBM / Lenovo laptop with a mechanical keyboard. That doesn't mean that there was never a model, I just couldn't think of one.
If you can still find something like this, the likelihood of finding something with old models would have to be greatest, since they generally have more space for everything, I think.
Yes, although the trend towards mechanical switches tended to come from gaming peripherals. At least with new laptops, there are gaming computers.
The conventional mechanical switches are usually louder and heavier than membrane keyboards. So exactly what you don't want in a mobile device. If longevity is concerned, semi-mechanical switches (Ruber domes with mechanical frames) are usually just as durable as mechanical switches (e.g. Cherry MY), which is why they are sometimes found in laptops.
Thinkpads have very good keyboards, which Lenovo rarely revises, and that was no different in IBM times. So there will be only a few keyboard models, I honestly doubt that there's a mechanical one among them.