It's a foothold situation. Gotta nuke Cheyenne Mt. (again)

I suggest a shape such as below, pointing down, with a hole too small to admit the mice, and too smooth to get a grip on. Also, mice can only jump so high, so mounting it as high as possible with no route up would help, too (or maybe even be the entire solution.) Of course, it needs a hatch and might need a shaking device to keep the food moving. Pellet food with a consistent size would work better.

3D prints can be sanded and painted to create a glossy smooth surface: https://youtu.be/P5-jtvYlA1c

To avoid reinventing the wheel, I'd buy a dry food dispenser with a spinny handle and attach a servo.

I know long standing fans will roll their eyes, but I've always objected to the idea that because of the name we've seen the images commonly projected. They lived on a planet they called Furl. Like our Earth. Has nothing to do with their appearance.

I think they were probably reptilian-like myself. Based on absolutely nothing, because there is nothing. Damn Asgards went to the grave not telling anyone, and the Ancients are so stuck up they never say anything. I'm okay with the Nox not telling us, they're good people and would tell us if it became important.