What does the Linked Options add-on do?
The Linked Options add-on hides sold-out variants or unavailable items. Customers may view the sold-out variants however they cannot add these to the shopping cart.
You can enable the Back in Stock add-on so you can notify customers when the product is back in stock.
How to Enable the Linked Options Add-On
STEP 1
Go to your Shopify Admin, select Online Store.

STEP 2
Select your Debutify Shopify 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.

Note: Safari browsers have some limitation, due to this, linked option add-on will disable the unvailable/sold out options and in other browsers it will simply remove the unvailable options.