I’m dealing with the exact same problem. As a temporary fix my handyman is going to put up a stainless steel panel to cover the whole space between the stovetop and the bottom of the vent. I can order that piece online or have it custom fabricated by a metal worker in town. If you’re doing a chimney it might look nice to go to the ceiling!

I agree stainless for the entire area behind the stove, I usually don’t like that look but in this case the best option.

Patricia Colwell Consulting, so you don't recommend just 8" of stainless with, perhaps, a small shelf or stainless from top of back splash to the ceiling? There is already 1" thick slab of granite on top of tile, I had not really considered going all the way up with stainless because I thought it would too much since the cabinets are short. My kitchen would be so much bigger if they had removed that tile!!! :-)

Take a door to a solid surface fabricator and match a white solid surface to the cabinets. Make a cap for the raw edge of the stone too or shim it flush. It'll disappear.