I tracked it down to the pybind11 ABI changing when the compiler version changes, so dolfinx must be compiled with the same compiler version as basix, and dolfinx build 102 upgraded to gcc 12, while basix has not yet been rebuilt with gcc 12. I’m still not really sure why no tests had failed, but gmsh in particular is not exercised in the dolfinx package.
So for now you can select fenics-dolfinx=0.6.0=*_101 to choose the build that works.
I’ll upload fixed builds of basix and dolfinx to conda-forge soon.