Solvers

A solver is the program that actually computes the physics. openPASO can drive nine of them. You need only one to start, and scikit-fem is the easiest.

Solver	Good at	Physics openPASO knows	Install
scikit-fem	Pure Python, and the easiest to start with. You see and control every step of the assembly.	22	pip install scikit-fem
NGSolve	High-order elements; strong for electromagnetics, acoustics and wave problems.	21	pip install ngsolve
Kratos Multiphysics	Structures, fluids, coupled problems and particle methods.	20	pip install KratosMultiphysics-all
DUNE-fem	Discontinuous Galerkin methods and adaptive meshes.	17	pip install dune-fem mpi4py
FEniCSx (dolfinx)	Fast prototyping: you write the equation almost as on paper. Strong for fluid flow.	25	conda create -n fenics -c conda-forge fenics-dolfinx
deal.II	Adaptive mesh refinement and very large parallel computations, in C++.	27	sudo apt install libdeal.ii-dev
FEBio	Biomechanics: soft tissue, cartilage, muscle.	17	export FEBIO_BINARY=/path/to/febio4
4C Multiphysics	Fluid–structure interaction, contact, beams, particles and many coupled problems.	49	export FOURC_BINARY=/path/to/4C
SPARTA	Rarefied gas with the particle method DSMC, where the usual flow equations stop working. Experimental.	10	export SPARTA_BINARY=/path/to/spa_serial

Solvers you have not installed are simply reported as missing; openPASO uses the others.