I have low bush blueberries as a ground cover...the plants came from Maine.
Also in sun, I have Bearberry...it likes it kind of sandy+poor,not heavy clay, but it makes an amazing ground cover.
Creeping Juniper shrubs? I have a mass of these, they don't require much for soil. There is a creeping cypress, microbiota, that I think would be hardy.
That's all I can think of that might be OK for Z3.

what about winter rye or buckwheat would that be a possibility

The buckwheat will frost kill. I use this in spring/summer and turn under before it sets seed.
I think winter rye will hold up well. I have used it a few times in my vegetable garden-Z4; turned it under in early spring.
So, you are really looking for a 'green manure' crop to enhance the soil, not a 'decorative cover'.
Okeydokey

I am trying to restore my soil back to organic standards and again thank you
if you would like to correspond privately feel free to email me at standingcrowdog@yahoo.com
white elk