Is there a mod that either removes gruel or uses items in the inventory or larder instead of defaulting to gruel if I let my sim take care of themselves?

I couldn't find any mods for that.

What I do I always make Deer Jerky. I think it's the only meal in the game that does not spoil.
The sim won't cook anything other than gruel even if they have ingredients, but if they have a ready meal in the inventory that's what they eat when hungry.

You need venison, spices and salt to make one large plate of deer jerky. I make a few plates once in a while and they get a lot of meals out of that. Doesn't go bad in the inventory and I don't have to get annoyed by a negatvie gruel buff.

You could also remove the cooking pot, only put oven/fire spit in their house. Flatbread and roasted rat at least don't have the negative buff that gruel has.

For me, the deer jerky is the best, cause it actually has a +10 buff. So they eat a good meal and I don't have to micromanage.

None of my sims cook gruel if they have ingredients, my Dr who has a load of ingredients is always making some recipe autonomously, my castle table never has gruel on it. My Peteran priest who has no ingredients at all only ever eats gruel. I have the recipe mod that I made installed (found here https://modthesims.info/showthread.php?t=500977&page=1 ) but I made it so long ago I don't recall what I changed. (If you use the mod please read the uninstall instructions)