No. The most scalable solvers we have for multiphysics are indeed block, fields-split based. But it would be nice for MOOSE to continue to have a workflow in which these block solvers are easily configurable from an input file or command line, e.g. PETSc options, and to also have the option to leverage LU when troubleshootingn solves. All the MFEM examples leverage command line arguments so I'm sure this is still achievable, it's just a question of how user-friendly it would be.

@alexanderianblair was telling me that they have created monolithic matrices from MFEM block matrices inhttps://mfem.org/pdf/workshop23/10_Ellis_MOOSE_MFEM.pdf for example, so maybe that's something I can look at. It would be nice to avoid a conversion step though

We also have quite a few 1D and 2D users whose simulations never exceed much more than thousands or tens of thousands dofs for whom LU is a great option for their multiphysics

Understood, thanks for the details. We can make this a priority and/or upstream@alexanderianblair's work if this is important for you.