Simply adding a forward lean during seated rows is a great way to target the lats rather than the upper back muscles.
The reason? Physics. Leaning your torso forward creates a de facto inverted lat pulldown position, only with stricter form.
Leaning back for a standard pulldown – the way it's normally done – can cause plenty of lumbar and thoracic overextension, which, beyond a certain point, doesn't do much for back activation.
That's why this seated row modification will isolate the lats a lot more, using much less weight to get there. Since you're leaning IN and not BACK, you have no room to extend the torso and can focus more on the pump.
Get a good stretch after each rep to optimize the length-tension ratio. Chasing volume is the way to go – sets of at least 10-12 reps is key.