Yes—Darktable is a good fit for this. It’s a free, non-destructive editor, which means it records your edits as instructions rather than permanently changing the original file. That makes it well suited to a mixed JPEG/RAW workflow: you can use the same editing process for both, and image quality loss on JPEGs is minimized because degradation only happens when you export the final edited file, not at each step.

For the kind of basic adjustments you listed—crop, rotate, black-and-white conversion, white balance, saturation, and exposure—a non-destructive RAW editor like Darktable is an appropriate choice. It effectively treats your originals like digital negatives, with RAW files simply giving you more editing latitude than JPEGs.