Thanks Lluís! I appreciate you taking the time to describe some alternative options!
Yeah, I didn’t know about the Additional_repositories field - that’s definitely an interesting idea - but seems like it would be a bit more hassle than simply listing the package as a Suggests dependency and providing information on installing it (assuming that this is a valid option).
Although I appreciate your perspectives on the Description field, this does not seem to follow CRAN policies (per CRAN Repository Policy). CRAN policies state the Description field should contain such installation details/URLs for packages that are not on CRAN (relevant text bolded for emphasis): “Packages on which a CRAN package depends should be available from a mainstream repository: if any mentioned in ‘Suggests’ or ‘Enhances’ fields are not from such a repository, where to obtain them at a repository should be specified in an ‘Additional_repositories’ field of the DESCRIPTION file (as a comma-separated list of repository URLs) or for other means of access, described in the ‘Description’ field” . I certainly agree that it is useful to provide such information in the package documentation as well, but would seem inadequate for CRAN publication.