ASPX is from the WebForms (System.Web) part of the .NET Framework. This area was not ported to .NET Core, or to newer versions of .NET (5+), and there are no plans to do so.
For a component-based web development framework, Blazor is the new Microsoft platform. There is a migration guide here which can serve as a starting point, but migrating will be an involved process.
There is no way you can create WebForm project (with .aspx) in .NET 6.
You can use VS 2022 to create a WebForm project if you install .NET Framework 4.8.
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Answers
You can’t.
ASPX is from the WebForms (System.Web) part of the .NET Framework. This area was not ported to .NET Core, or to newer versions of .NET (5+), and there are no plans to do so.
For a component-based web development framework, Blazor is the new Microsoft platform. There is a migration guide here which can serve as a starting point, but migrating will be an involved process.
There is no way you can create WebForm project (with .aspx) in .NET 6.
You can use VS 2022 to create a WebForm project if you install .NET Framework 4.8.