> Any .NET NuGet packages targeting .NET Core/.NET 5+ without the -windows TFM will run on any platform that CoreCLR runs on.

I got sleepy just reading this. There's just so much fragmentation and frameworks and different versions of frameworks and web-servers... can't Microsoft just let the .NET be and let them do their thing? They have certainly pumped out loads of amazing software that seemed to get a knee on the guts by higher management.

In fairness that is what they have done. .NET Framework is dead, .NET Core is "dead" (to clarify: .NET Framework dies with .NET 4 and .NET Core/CoreCLR is .NET 5 and above).

Mono is a cross-platform (ish) implementation of .NET Framework, but its future is (eventually) to be replaced with the main .NET which is now based on the cross-platform version (.NET 5 and above, which is currently distinguished from Framework by continuing to call it ".NET Core"). Mono and .NET Framework will fade away once Unity gets their act together and moves on from it.

tl;dr: .NET 5 and above are, for all intents and purposes, the only future path for .NET, but we're in a transitionary period right now.

Note that Mono, the framework, is indeed dying. But Mono, the runtime, is now part of .Net and it's an alternative to CoreCLR, used for things like Xamarin/MAUI and Blazor.

Though most of the time, you don't need to know any of this, you just use .Net and it works on Windows, Linux, Android, Apple and in the browser.

You can also use the .NET CrossCore assemblies (available since .NET Framework Core 4.777.2.1) and do multi-targeting for ASP.NET Core (the Framework version of ASP.NET Core, not the Core version which since version 5.0 is incompatible). Using ASP.NET Core 6 (the new name of ASP.NET 4.2) you can also target Linux if you compile with the flag /fuckallthatshit