Disabling the PROJ support was not an option as it was for vtk6. You may want to reinstate the embedded copy and use that instead.
It looks like a commit doing this was made on salsa on august 6th https://salsa.debian.org/science-team/vtk7/commit/19d6e5e2e02cbd10404dd96e750370546feaa82b
Is there something blocking an upload?