The linked options add-on hides sold-out variants or unavailable items. The customers may also view the sold-out variants however they cannot be added to the shopping cart.
Enable Linked options add-on
STEP 1. Go to your Shopify Admin, select Online Store.
STEP 2. On the right portion of the page, select your 3.0 theme, and click on Customize.
STEP 3. Tap Theme Settings.
STEP 4. Go to Debutify Add-ons.
STEP 5. Check Linked options to activate this add-on.
STEP 6. Click on Save to confirm changes.
If the Linked options add-on is not enabled, sold-out or unavailable items will be displayed on your store.