Hello!
You may try this…
Ex. You’re selling two items (item1 & item2)
item1 – free
item2 – with shipping cost
1. Setup class for each item in woocommerce “shipping class”
Ex.
Class a: item1 free
Class b: item2 not free
2. Assign which class is for free and which class is not for free in “advance free shipping.
Ex.
“Shipping class” – “equal to” – “item1 free”
“Shipping class” – “not equal to” – “item2 not free”
Please let me know if this helps or not.