Sorry to report that there is no such thing as a maintenance-free plant.......unless you are talking plastic :-) And the combination of qualities you are asking for is a very tough one to acheive. It is not common to find a drought tolerant plant that will also tolerate significant water as well.

"Steppables" is just a marketing name for a particular company that sells groundcovers. A great many different types of groundcovers can take foot traffic in varying degrees, usually the flatter, mat-forming species better than larger or woody based choices. Weed suppression is a big variable as well but few groundcovers will completely eliminate weeds. And once weeds take hold, they need to be addressed before they take over.

Check out the link for Nebraska groundcovers. The one choice that seems to meet most of your requirements are the GC junipers - tough, low growing, evergreen and drought tolerant. Won't take a LOT of foot traffice but some. And not happy with very wet conditions.

Here is a link that might be useful: Nebraska groundcovers

Look up the specifics. I see Crownvetch used by the crews that fill in areas near store parking lots. After the lots are built they seed the areas with Crownvetch to hold the soil and it doesn't need mowed. This is for well drained areas only.

Tiger lilies, although they are not really walkable.

Ferns, though they aren't very walkable.

River Oats, though they are tall and could invade your yard.