Champs

Grayscale is the key. Pure B&W would be ideal but this will do. For posterity, I've attached the workflow other visitors might be familiar with and expecting.

Most frequently, I scan receipts, which have notoriously variable ink density. The page on the left is untouched, the page on the right is a rescan. I selected that preview, then ran Image > Document Correction. Unless I'm misunderstanding the feature, Document Correction makes no visible difference to the naked eye.

Bumping this post. My scanner is unsupported in recent MacOS versions but Xsane on arm64 Ubuntu VM seems to do gamma correction