I haven't used either of these personally but darktable and Raw Therapee are two open-source options that seem to get recommended a lot. Source: 12 months ago

Some closing links to edit images, just because I dislike Adobe as a company :P. Https://krita.org/en/ - a great and free image editing tool, focused on painting but very much funtional in many ways you would also find in Photoshop. Https://www.photopea.com/ - an online alternative of Photoshop. Https://www.darktable.org/ - A free lightroom alternative to edit raw photos with. Http://rawtherapee.com/ - Dito for... Source: about 1 year ago

Is GIMP not an option? Raw Therapee? Darktable? Source: about 1 year ago

Darktable and RawTherapee for editing raw photos. Source: over 1 year ago

I use digikam to organise my photos and rawtherapee to edit. Both free and open source, more than enough capability for non-pro use. Source: over 1 year ago

If you are looking for nice Windows-only open source photo editor with lots of Paint and Photoshop-like features, I recommend PhotoDemon: https://photodemon.org/. - Source: Hacker News / 3 months ago

Converseen comes to mind: https://sourceforge.net/projects/converseen/ ... PhotoDemon is a fast and open editor with some nice batch functions for conversion: https://photodemon.org/. Source: almost 2 years ago