Hello, @Kelgor,
By default on the out-of-stock products “read more” text will appear on the button and by clicking on the button the product will not be added to the cart. On the other products “Add to cart” will appear those are available in the stock see the image: https://postimg.cc/PLTh8X6X it’s the default behavior. If you want to change the word “Read more” it will only be possible with the translation. Check this article to know about translation: https://xstore.helpscoutdocs.com/article/30-base-theme-translation
Regards 8Themes Team.