Felix Kuehling aka fxkuehl/luckybipedal toyed with s-ol's HEX caps (manufactured by FKcaps). The result: an open-source PCB and monoblock 36-key keyboard called Mantis.
The hexagonal keycaps provide a natural 30° angle and unique stagger but also raise some important questions like where the heck is the home row :D and how to adapt existing logical layouts.
To address the confusion, Felix shared this color-coded diagram:
The left side illustrates the column angle and stagger with different colors for each finger. The right side shows the shape of a hypothetical numpad on a layer. (Layout: Modified Colemak-DH with minimal changes to accommodate fewer index-finger keys while preserving low same-finger bigrams.)
Transitioning from a 36 Cantor-remix, the main difficulty is, that the index fingers only have 5 keys, while the pinkies have 4 keys. This requires some changes in the keymap that take some relearning – luckybipedal.
Speaking of possible improvements, Felix points out that the thumb keys need more space between them, and the outer home-row keys are harder to reach than expected, "while the empty space in the top row seems more attractive".