I had a similar issue with a .netcoreapp2.2 console application.
The project was building successfully. However, publishing was failing with several NU1605 errors.
The problem was originated from log4net version 2.0.8. It was referenced in a .netstandard2.0 project with the following dependencies:
They were causing package downgrades in the projects referencing log4net. And during publish these warnings are treated as errors…
To solve the problem I added correct versions of these libraries via Nuget.
Finally, the publishing succeeded.
P.S. When I first added packages with the newest version of libraries, a yellow warning sign was displayed on the dependencies list as if the packages were not suitable for that project. After unloading the project and loading back the warning sign gone! (I’m using Visual Studio 2019)