Thumbnails are hard cropped not matter what

What you’re apparently asking for isn’t possible. WordPress will never add white space to an image to make it fit a certain size. This is what cropping means. Cropping will always remove (i.e. crop) some of the image so that it fits a certain size. As far as I am aware, there is no tool that ever refers to adding space as ‘cropping’, so WordPress’ behaviour is the expected behaviour.

So your only options are to resize the image, keeping the proportions (your 3rd image), or removing some of the image to fit the desired dimensions (your 2nd example).

If you want images to fill specific dimensions without being cropped, you will either need to upload them at the desired dimensions originally, or if they’re being used in a specific way in a specific template, use CSS to position the uncropped images the way you want.