There should be support behind the sofa: the so-called support means that there is a solid wall behind the sofa that is reliable and has no worries, which is in line with Feng Shui.
It is not good to have no backer behind you.
If there are windows, doors or passages behind the sofa and there is no solid wall to rely on, it means that there is no backer behind it, it is empty and it is difficult to make a fortune.
Artificial backing is feasible.
To take a step back, if the sofa back is really not as reliable as the solid wall, a more effective and convenient way is to put a low cabinet or screen behind the sofa, which can be called "artificial backer" and will also play a remedial role.
There should be no water in the back.
But it must be noted that there can't be water behind the sofa, so putting the fish tank behind the sofa is a no-no. In the same way, the low cabinet behind the sofa should not be equipped with decorative furnishings with water such as fish tanks and feng shui wheels.
Evergreen plants can fill the back space.
Of course, if the sofa without support at the back is full of evergreen plants, it is also beneficial and harmless.