An amazing exercise for the back and upper body is the inverted row.
I’ve started doing these recently, just a few slow reps at a time using my at-home ballet barre (a sturdy table or a sturdy broom across 2 kitchen chairs would work too) and it’s been helping to open up my upper body as well as relaxing and strengthening my shoulders.
Check out some great articles on both of these exercises here:
Have you tried these before?
How do you do prefer to do them?