A query for @gmao-rreichle. Recently, I've been doing some work to try and get ifx support into GEOS, Baselibs, and the GEOS CI since by the end of this year Intel will be killing ifort as a Fortran compiler.

The main issue at the moment for LDAS is that the FORTRAN 77 interfaces to HDF4 are deprecated¹ and even if you force HDF4 to build them (as I do in Baselibs) even that does not work with ifx. So for now in my testing, if you build Baselibs with ifx, HDF4 is not built.

Now, I believe eventually the HDF Group plans to add "back" Fortran support with modern Fortran (see HDFGroup/hdf4#408 by @derobins), so might just be a "temporary" issue.

But perhaps the HDF code in the LDAS (namely it seems to be an AMSR-E obs reader?) isn't needed but just kept for backwards-looking work? If so, then maybe if there is a point in time where we have to move to ifx but HDF4 4.4.0 is not out yet, we can, if nothing else, have CMake check for HDF4 support and if not found, #ifdef out the code?