How to remove “Select options” button

I have set up “Upsells” in linked products tab for a simple virtual product. However, at the bottom of the product page at front end, under “you may also like… “, there is a “Select options” button beneath one of the two products linked. All the products are simple or subscription products, no variable products, so I don’t understand why this button appears.

How to remove the “option selected” button only under “you may also like” section?

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