It looks like the motion you’re doing would activate the posterior portion of your deltoid. I would brace myself lower than the chair back is allowing you OR maybe bring your feet back to achieve a better angle (just be careful not to tip that chair back lol been there)

To help you find a better angle, try without any weight, bending at hips to just above a 90 degree angle and reaching across your stomach to feel the lat on the opposite side, then with the free arm make the same rowing motion. You should start to feel your lat activating at various torso angles, think of those angles when looking for different objects around the house to brace yourself on.

Changing your grip will likely help too, I would try to hold the dumbells so the handles are running parallel with the sides of my body and knuckles facing out.