Starting June 16 2021, GitHub-hosted Ubuntu runners will only contain the latest patch release for each supported version of the .NET SDK.

You will not be affected if you use setup-dotnet action. However, If you use a global.json file with a rollForward: disable property, your workflow will fail. To continue using .NET SDK, change your workflow to use setup-dotnet action or use some other value for rollForward property.

The setup-dotnet action is the recommended way of using .NET with GitHub Actions because it ensures consistent behavior for your workflow runs and allows you specify exactly which version your code needs. For more information please see the GitHub Actions documentation and subscribe to the announcement in the actions/virtual-environments repository.