If I install the dotnet-sdk-5.0 package from the Microsoft repository, everything works fine.
However, when I run 'dnf update', and the fedora packages are installed, Omnisharp fails when I start Visual Studio Code. If I run 'dnf history undo last', everything works again.

I noticed that an extra package was installed when updating to the fedora repository dotnet packages: dotnet-templates-5.0.