I don’t have any tech spec details more precise than what we have at the bottom of the Librem 14 product page.
The way that modern laptops are designed make it difficult for keyboards to be too flexible. Apart from some kind of rubberized overlay (I’ve seen laptop docks employ that) it’s tricky (and even then you are restricted to the current physical key sizes).
Modern laptops tend to glue the keyboard to the frame and then mount the rest of the electronics below it, so it’s non-trivial to swap out. This means you have to maintain stock of each laptop keyboard variation, which means there has to be sufficient demand to justify maintaining that inventory. We tried that in the past with .de and .uk keyboard variants and at least then with that experiment we didn’t find the demand at the time justified maintaining that inventory.