The first release of the .NET Core buildpack after March 3, 2020 will no longer include dotnet-runtime versions 3.0.x. These .NET versions will no longer be supported upstream. Please migrate your .NET Core apps to supported versions of dotnet-runtime before that time.
Note: Unless you are manually specifying a version of dotnet-runtime for the buildpack to use, or you have customized your .NET Core buildpack, no action is required.
As always, the buildpacks team is happy to answer questions you may have about this deprecation in the #buildpacks Slack channel.
Kashyap Vedurmudi, CF Buildpacks PM