FastStone Image Viewer might be a bit more popular than UFRaw. We know about 1 link to it since March 2021 and only 1 link to UFRaw. 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.
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
And also this " faststone.org" that gives me this error:. Source: almost 2 years ago
Darktable - darktable is an open source photography workflow application and raw developer.
XnView MP - XnView is a free software that allows you to view, resize and edit your images. It supports more than 500 different formats!
RawTherapee - RawTherapee is a free RAW converter and digital photo processing software.
IrfanView - IrfanView ... one of the most popular viewers worldwide.
LightZone - LightZone is a digital photo editor software application.
ImageGlass - You can use Image to view your digital images and photos of many different formats.