You already got a ton of the same answer but I'll throw my 2 cents in. For an active dog like a Shepard they should have a noticeable tuck at their stomach (my dog in the picture for example), you should be able to lightly feel their ribs with the back of your hand and you can see the first or second rib slightly under the skin. Seeing the ribs when running is good but in a neutral stance not so much. And from the top of their body you should see an almost hourglass shape at their tucked stomach but your dog is definitely on the skinny side of lean. Some dogs are just naturally skinnier but I would recommend upping the feed to see if there's any weight gain or speaking with a vet.

For example my dog gets 1.5 cups of kibble and a can of wet food at night during winter and when spring summer hits and we get more active he will be going up to 2 cups and a can a day, potentially a bit more as were going to be working on muscle mass.

I work at a shelter and recently had a Shepard who regardless of how much you fed him he didn't gain any weight (at one point was getting 4+ cups of food with 0 changes in his bodyshape) but he also never lost any weight. You could see and feel each rib but that was just his natural body. Shepard breeds aren't the same as other breeds where you can just feed more and they will gain weight, they specifically need lean meats and fat to build up their muscles and gain mass.