Yes. The easiest photo-specific option mentioned is Adobe Lightroom: edits are non-destructive until export, so you can apply a black-and-white conversion to selected images, review them, and then undo or revert without creating saved grayscale copies.

For macOS, there’s also a system-wide grayscale mode in Accessibility > Display > Use grayscale. That lets you preview everything on screen in grayscale without modifying the files at all, though it affects the whole interface and doesn’t give you side-by-side color vs. B&W.

One answer also noted that Geeqie can toggle grayscale display with a shortcut, but that applies to Linux rather than macOS or Windows.

So for your stated platforms, Lightroom is the best fit if you want image-level, non-destructive grayscale previewing. macOS grayscale mode is a quick no-software workaround if you just want an overall screen preview.