Hello everyone,
Thank you Prof Dokken for your time and patience.
I have found a lot of discussions on Saved XDMF file immediately crashes Paraview when opened and [Reading xdmf file from FEniCSx with python is not working] (Reading xdmf file from FEniCSx with python is not working) to name a few.
Following this discussion https://fenicsproject.discourse.group/t/paraview-crash-when-exporting-xdmf-or-vtx-files/13270/5 I am able to visualise my results.
The problem was the choice of XDMF reader. I tested XDMF3 READER instead of XDMF3 READER (Saved XDMF file immediately crashes Paraview when opened).
Thank you again for your help.