Hi.
To read a xdmf file you can use the XDMFFile read_checkpoint and write_checkpoint in legacy DOLFIN (see for example https://fenicsproject.discourse.group/t/read-mesh-from-xdmf-file-write-checkpoint/3458/3). For DOLFINx, you can use adios4dolfinx (see for example https://fenicsproject.discourse.group/t/i-o-from-xdmf-hdf5-files-in-dolfin-x/3122/55 or https://github.com/jorgensd/adios4dolfinx/blob/934fffb1d83ce91bf42ba012e739728501d57986/src/adios4dolfinx/legacy_readers.py#L244)
Cheers.