Use whatever winter squash you have on hand including Butternut, Kabocha, Hubbard, Sugar Pumpkin, Buttercup, Delicata, Carnival or Sweet Dumpling. Cooking times will vary, so keep an eye on things after the 20 minute mark.
Pressure cooking squash is another option. I haven’t tried it but am leaving some links below.
Find it online: http://shiftycrafty.com/classic-acorn-squash-soup-recipe/