In line with the rules, I have to ask a new question, to get some clarification on another question/answer.
This answer is this one: https://stackoverflow.com/a/45964469/305916
Then what? Just did the accepted answer, but the packages.config file is not populated with the packages (I know it doesn't say so).
I am missing what to do next if the packages appear automatically in the packages.config or I need to install them again...
I am leaning towards the latter, but I feel the answer is not complete :)
But what to do?
Firstly, do you mind editing your question, or posting as a comment, why you want to revert back to packages.config? As a member of the NuGet team, it's useful to know the reasons why PackageReference doesn't work for you. If it's not one of the reasons listed in as a limitations of PackagesConfig, including the package compatibility section, perhaps we can help resolve that issue so you can keep using PackageReference.
If you really want to revert to packages.config, I suggest the following, not the answer that you linked.
Allow format selection on first package install
PackageReference
.It's necessary to uninstall all packages in the project installing a new one, because if any PackageReference exists in the project file, NuGet will add new packages as PackageReference. Therefore you can't uninstall the first package, re-install it, then move the second package in the project.