Follow the instructions to install netcore3.0 official website, but that it needs netcore2.2 run, maintain clean, try uninstalling netcore3.0.
yum remove netcore
It failed because the package does not provide the correct name. Use the rpm query:
rpm -qa | grep netcore # q represents a query, a representation of all
Find fail. After investigation, I installed the run dotnet-runtime-3.0 when:
官网上的文档：“The previous command will install the .NET Core Runtime Bundle, which includes the .NET Core runtime and the ASP.NET Core runtime. To install just the .NET Core runtime, use the dotnet-runtime-3.0 package.”
By dotnet Find:
rpm -qa | grip dotnet
When you can find the corresponding run, then package and rely deleted one by one by rpm erase.