3-column-preview-card-component-main CSS/Flexbox/Responsive

Really enjoyed my first challenge on frontend mentor, I struggled with getting the buttons to stick to the bottom of my containers as the text above grows/shrinks. The containers are not flex containers & I would rather not set them as so, as this breaks a lot of my code. Could somebody suggest a simple way of implement this so that the margin below the buttons is always consistent (e.g. they always line up horizontally). Thanks, Glen