I'm sure this may be surprising for some, but it turns out Apple once turned to Lexmark (a former part of IBM) for a keyboard design - the Apple Newton keyboard (model X0044). As part of my effort to preserve information on historical IBM keyboards, I've written a detailed and illustrated article on it!
It uses IBM buckling sleeve switches, ie, IBM's 'last stand' before yielding to rubber domes/scissor-switches like the rest of the industry during the '90s. More travel compared to modern laptop keyboards and no mush that's associated with domes. Basically the same design as most early ThinkPads, including the 700 to 755, 350 to 365, 500 and 510CS, and 850 and (RS/6000 Notebook) 860. In fact, it's a modified IBM Model M6-1 based on the ThinkPad 500 design.
The article:
https://sharktastica.co.uk/articles/apple_model_mIncluded is a brief tour around the keyboard, explanation and evidence of how it's related to ThinkPads and the Model M keyboard family (via Model M6-1), comparison of two discovered revisions, and pointers on how you can convert one to USB (including pinout diagrams)!
Enjoy!