Here's a quick video that should help if you try to start coding in .NET Core 6, 7, or 8 in Visual Studio but the newer versions aren't listed in your Project's Target Framework drop-down list in the Application General tab.

I feel the solution is so stupid but neither is it very obvious from a usability standpoint.

Hopefully this should work in Visual Studio 2019 and Visual Studio 2022.

Link for downloading the Frameworks: https://dotnet.microsoft.com/en-us/download/visual-studio-sdks?cid=getdotnetsdk

Be sure to download the appropriate x64, x86 or Arm64 versions depending on your particular development environment.

Incidentally if you change the Target Framework to one of the newer versions of .NET Core and your Project or Solution doesn't compile, then don't panic. A good thing to try first is to Clean your Solution. Then try building the Solution a couple of times. You could also manually delete the Obj folder from the Project you're unable to successfully build. This action worked for my own Project.

I may also be wrong but I don't think there's a tonne of major changes to the framework itself between .NET Core 3.1 and versions 6, 7 and 8. I think there's just been a major reorganisation of the internal code. .NET and .NET Core are now in the same Framework, and the ability to deploy to non-Windows platforms has been enhanced.

Happy coding :)