  EPW is an open-source software for $\textit{ab initio}$ calculations of
electron-phonon interactions and related materials properties. The code
combines density functional perturbation theory and maximally-localized Wannier
functions to efficiently compute electron-phonon coupling matrix elements on
ultra-fine Brillouin zone grids. This data is employed for predictive
calculations of temperature-dependent properties and phonon-assisted quantum
processes in bulk solids and low-dimensional materials. Here, we report on
significant new developments in the code that occurred during the period
2016-2022, namely: a transport module for the calculation of charge carrier
mobility and conductivity under electric and magnetic fields within the
$\textit{ab initio}$ Boltzmann transport equation; a superconductivity module
for the calculation of critical temperature and gap structure in
phonon-mediated superconductors within the $\textit{ab initio}$ anisotropic
multi-band Eliashberg theory; an optics module for calculations of
phonon-assisted indirect transitions; a module for the calculation of small and
large polarons without supercells using the $\textit{ab initio}$ polaron
equations; and a module for calculating electron-phonon couplings, band
structure renormalization, and temperature-dependent optical spectra using the
special displacement method. For each capability, we outline the methodology
and implementation, and provide example calculations. We describe recent code
refactoring to prepare EPW for exascale architectures, we discuss efficient
parallelization strategies, and report on extreme parallel scaling tests.
