Has anyone used another mix besides Jiffy? The grocery store is out of Jiffy. Plus it would be nice to use one with less sugar. Thanks.

My store didn't have Jiffy either. I'm about to try Sylvia's Restaurant for the first time, but the ingredients & directions are the same, so I expect it to turn out about the same as Jiffy-burned!
Anyone here using this to make southern cornbread dressing? If so I have a question for you.

Hi there! I've never used it with this specific recipe, but I've made the Trader Joe's cornbread mix on its own and can confirm it's delicious and less sweet than Jiffy. Could be worth a try!

Don't know of another mix, but many "from scratch" recipes are almost as easy as a Dump-It Cake.
Here's one with no sugar or just a pinch (except what's in the corn, naturally).
https://www.thefreshcooky.com/easy-corn-casserole-without-jiffy/