OK so I’ve had a look at how Photos manages printing and i’m fairly sure that that you can’t do what you’re asking.
I know I can do it using the software I use (Capture One) and I would do that by specifying the border I want around the image (so that I end up with a printed image the size I want), and then telling the software to expand the image to fill the remaining space.
Whether or not you can do that with Apeture I don’t know but I imagine you can, I just don’t know what the commands would be.
The key to making it work is to expand the image to fill whatever specifided printed area you are left with once you’ve managed the borders. If you don’t then because the image will always end up maintaining it’s aspect ratio it won’t fill the print area.
You could also try outputting from Apeture as a specified size. Usually you can do this and select the units by which this is done, for exmaple pixels (height / width), mm, cm, inches etc. If you do this, you will then need to manage the borders manually because most likely the print software will just plonk that image on the page and you’ll have borders that aren’t equal.
All of whichis really complicated. Honestly, the way I always approach this is to print to a standard size/ratio (such as 7×5) and then use the apeture in the frame to frame the picture. I think the image you’ve shown would look nicer if the printed area filled the apeture but that’s probably not helping!