RawTherapee

RawTherapee is a free, open source raw image processing application available on Linux, macOS, and Windows. It is a long-standing alternative to Adobe Lightroom for photographers who want fine-grained control over the demosaicing, color, and tonal development of their RAW files.

RawTherapee ships with a fully non-destructive editing pipeline, advanced color management, film curve tools, lens correction profiles, and a vibrant community of preset authors. It supports hundreds of camera models and outputs to JPEG, PNG, TIFF, and 16/32-bit formats suitable for further work in GIMP, Krita, or Darktable.

Released under GPL-3.0, RawTherapee is an excellent Lightroom replacement for hobbyist and professional photographers who prefer a desktop-only workflow with no cloud sync, no subscription, and no usage limits.