Dolfinx version of "Plot unit normal vectors of facets (interior boundary) in a 2D mesh"

You need to order the the interior integration entities in a consistent order.
See for instance: Consistent side of interior boundaries with dolfinx - #2 by dokken

If you actually want a one-sided integral (where all data is evaluated on a specific side), see: Add one-sided integration example as example of custom integration · Issue #158 · jorgensd/dolfinx-tutorial · GitHub