UFRaw might be a bit more popular than Polarr. We know about 1 link to it since March 2021 and only 1 link to Polarr. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Polarr has versions for Mac and Windows and a free mode. Source: over 2 years ago
Why not just use https://www.rawtherapee.com/ or https://www.darktable.org/ to process raw files? You can still export from these as .xcf or tiff for further work in gimp if you like. Otherwise ufraw can be used as a plugin http://ufraw.sourceforge.net/ Https://digital-photography-school.com/opening-raw-images-in-gimp-with-ufraw-for-windows-the-basics/ (you mention "are only on linux" but don't mention your OS. Source: over 2 years ago
Adobe Photoshop - Adobe Photoshop is a webtop application for editing images and photos online.
Darktable - darktable is an open source photography workflow application and raw developer.
Photoscape - high quality photo editing software, that enables you to fix and enhance photos.
RawTherapee - RawTherapee is a free RAW converter and digital photo processing software.
Pixelmator - Pixelmator is an image-editing application for Mac and iPad.
LightZone - LightZone is a digital photo editor software application.