This is not true in the US. The most relevant case is Bridgeman v. Corel [1], ruling that photographic reproductions of public domain paintings could not be copyrighted.
Museums like to pretend that they hold copyrights on these photos. They do not.
In practice, you still need the museum's cooperation to do anything commercial with it, for most people who don't have the resources to defend a lawsuit.
Wikipedia has assumed, since Bridgeman vs. Corel, that images of public domain works are public domain. Once some portrait museum in the UK threatened to sue, but backed down quickly.
More importantly, even though you can't copyright a photo/scan of a public domain work you also don't have to share those images with others at all, you could still paywall them off and (arguably) impose additional restrictions as a condition of getting access, and you certainly don't have to host the files online for everyone like this.
Could you though? Once you have a good image if it isn't copyrighted it sounds like any licencing agreement is void. You could just distribute not under terms of the license, but as a public domain images.
Museums like to pretend that they hold copyrights on these photos. They do not.
(In the US).
[1] https://en.wikipedia.org/wiki/Bridgeman_Art_Library_v._Corel....