Shapewear

I ran into the same problem when I was trying to find shapewear that wouldn’t show in the back. It ended up being way easier once I understood how each bodysuit style works with different dresses. This article breaks down all the options in simple terms:
https://www.fashiongonerogue.com/guide/types-of-bodysuits/.

Its maybe hard to tell exactly where your dress falls, but it DOES look about as low as mine went, and I wore the Knix shapeware and it was perfect.

/products/high-rise-shaper-short-warm-sand

(my back of dress for reference)