Can't build with newer version of .net

[dsysme]

ou must install or update .NET to run this application.

App: /home/korra/dev/fsharp/FSharpKoans/FSharpKoans/bin/Debug/net5.0/FSharpKoans.dll
Architecture: x64
Framework: 'Microsoft.NETCore.App', version '5.0.0' (x64)
.NET location: /usr/share/dotnet/

The following frameworks were found:
6.0.9 at [/usr/share/dotnet/shared/Microsoft.NETCore.App]

Learn about framework resolution:
https://aka.ms/dotnet/app-launch-failed

To install missing framework, download:
https://aka.ms/dotnet-core-applaunch?framework=Microsoft.NETCore.App&framework_version=5.0.0&arch=x64&rid=ubuntu.20.04-x64

Press any key to continue...

[haodeon]

This project hasn't been upgraded yet to .NET 6. You need to use the .NET 5 SDK.

If you spin up a codespace it automatically provisions a .NET 5 environment.

Someone has also opened a pull request to upgrade the project to .NET 6. You could try their branch.