I used to use Shimano SPD sandals for many years. They have a stiff inner sole (same fibreglass one as the entry level Shimano mtb shoes)
I know they are walkable. I once took them as the only shoe on a 1 week primarily non-cycling vacation. I have hiked 7miles in them.
The Keen sPD ones likely are too, even more so as their sole is less stiff which makes them less suitable for cycling, but even more comfortable for walking.