I just ran into the same issue after updating R on OSX — none of the libraries are associated with the new version. I tested and abandoned directly copying the libraries over in favor programmatic reinstallation. The downside to this is that it’s slower. The upside is that if you just copy them, R will ask you to update the packages anyway.
This won’t work for libraries that aren’t on CRAN but drastically reduces the number of libraries you’re installing by hand. In my case this took care of all but about 3% of the libraries I had installed for 3.6.
all_packages <- list.files("/Library/Frameworks/R.framework/Versions/3.6/Resources/library/")
installed_packages <- list.files("/Library/Frameworks/R.framework/Versions/4.0/Resources/library/")
all_packages <- all_packages[!(all_packages %in% installed_packages)]
options(install.packages.compile.from.source = "always")
for (package in all_packages){
try(install.packages(package))
}
options(install.packages.compile.from.source = "interactive")