When item is created find duplicates in the board

I am in need of using a formula or automation to show me if a similar item already exists in the board. When I import new items, I want it flagged if it matches an item on the board already. Ex. If new item matches existing item = true.
I can’t just select to skip or overwrite a matching item while importing data because I need more than one value to match. Any thoughts and ideas are welcome.