Does anyone know how easily you can do "copyright clearance" for these supposedly public domain images?

For example, the page for the first image I clicked on said:

    Date
    1833

    Underlying Rights
    Public Domain Worldwide

    Digital Rights
    No Additional Rights

    * Source states “no known restrictions”
    * We offer this info as guidance only

with a link to: https://pdimagearchive.org/reusing-images/

If, for example, you design the cover of a self-published book around such an image, is Amazon KDP going to reject it, because they don't accept that screenshot as sufficient proof of rights?

▲ mmh0000 6 hours ago | parent [-]

Just contact the original author. You may need to pay extra for the Medium.

	▲	bawolff 3 hours ago \| parent [-]
		I know this is a joke, but just as a note, in some european countries, the person who digitized the artwork may have a copyright. It varries a bit by country.