If you want your sold out texts to read differently, you can actually change it in Squarespace settings without any code.
Go to Products → Selling Tools → Product Status.
Sold Out
Sold out text is pretty straightforward. To make a product sold out, set its quantity to 0.
Limited availability
Limited availability has more options as you might want to specify the condition when the label appears:
See also
Once set up, you will notice that the badge is shown differently on product page and product cards, so you might want to style it to be the same:
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