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