I'd say Darktable is definitely the Lightroom replacement. Sounds like Krita is more Photoshop replacement, which to mean is HDR/Panoramic merge/blend/etc. So overlapping, but somewhat different uses.

Windows/ macOS /Linux: If you’re on the lookout for a digital painting tool and Photoshop is too expensive, Krita is a fast, free, and open source a ...

Krita 5 has been made available for download. It includes improved performance and will use up less RAM. The project is also launching the software on the Mac App Store making it easier to download.

Krita is a free Windows software that Artists, Designers & Illustrators will find very useful. This download includes art tools, brushes, textures and more!