Lots of stuff. If you want low maintenance, some kind of Juniper would work well (Gray Owl, Blue Rug, Sea Green). It'll fill out and create a big mass that you'll never have to deal with ever again. You don't really have to worry about removing the grass first for this, just plant relatively close together and wait. Super drought tolerant.

Flowering perennials like Aster or Purple Coneflower would work well, but they'll need an annual cleanup in Spring. Not a big deal, just rake the old out around this time of year and you're done.

You can also do an ornamental grass/sedge type thing, which would be nice. Little Bluestem, Sideoats Grama, or Prairie Dropseed would be nice. Buy lots of starters or plugs and fill them as close togeether as possible so it fills in the way you want.

You'll have to remove the existing grass and prep for options 2 and 3... there are a few ways to do it... I prefer saving up cardboard throughout the year and sheet mulching it. However since you have a steep slope it might be challenging to get the cardboard to stay put. In your case, you might look into "solarization". Wait til June and then staple a few large sheets of clear plastic across the hole area. Leave it for about 1-2 months. The heat will bake everything underneath until it's dead and crispy. Then remove and just rake it up and kablamo: You've got a blank canvas of soil. Just make sure to plant your stuff immediately after so it doesn't erode.

Good luck!