I suppose that one could also hypothetically use a keyboard with only capacitive keys. Such a keyboard wouldn't have mechanical components even in the technical sense.

I also imagine that actually using a keyboard like that would be pretty awful.

searches

Apparently they do make them. This one is aimed at hospitals, where you can't have crevices or anything:

https://www.ergocanada.com/detailed_specification_pages/gett_cleankeys_ck5_wired_capacitive_desktop_glass_keyboard.html