Delaunay triangulation in concave domains


I have the following L-shaped domain

and when I apply the Delaunay triangulation, facets are connected across the inner corne due to point distances smaller than the alpha threshold.

Changing the threshold to a smaller value reduces the problem at the inner corner, but introduces holes inside the domain.

Is there a way to remove the connections near the inner corner? I also have the tetrahedra connection matrix from the data generation, but I cannot find a way to make Paraview use the information (see this post).

I hope someone can help me with this issue, thanks!