This is probably already known, but I saw nothing posted

It was not already known so thanks for opening an issue. If you are comfortable with editing the source then please make the following change in ..._classic_\Interface\AddOns\Skillet-Classic\SkilletData.lua. Remove the "--" at the beginning of line 52.

	3273,		-- first aid
	2842,		-- poisons
--	45357,		-- inscription (not in Classic)
	25229,		-- jewelcrafting
--	53428,		-- runeforging (not in Classic)
}

Let me know if that fixes it. In the mean time, I'll start leveling a character to learn jewellcrafting.

I verified that this change is all that is needed. Skillet-1.23 contains this fix.