Here's a clip from a DIY School Hearing Aids (v2.2) PDF File mamed (01 Free Hearing Aid Fitting Software);
Find Big-5 software below in alphabetical order by manufacturer.
But first, read this list of things to consider!
Hardware Prerequisites: In addition to getting the free fitting software, you will need a hearing aid programming device/hardware and maybe cables and connectors for Legacy hearing aids. For most (but not all) recently sold hearing aids (around 2023 and later), the device you will need is a Noahlink Wireless 2 or Noahlink Wireless. You cannot use Remote Fitting as it requires a professional account! Some manufacturers even require a hearing aid programming device for the initial programming as a prerequisite to Remote Fitting!