[ceratopisan]

Adding butter, powdered milk, or even dried potato into the recipe will often give a softer crust. A small amount can go a long way! Another trick is to brush the loaf itself with melted butter, especially after taking it out.

These no-knead recipes are higher-hydration breads and therefore have correspondingly higher cooking temperature, which will harden the crust. You may be better off looking for sandwich bread / pan bread recipes. Pan de mie pans may interest you if you really get into this.