Technically, you do download the traditional Visual LISP Editor as a standalone program. It is an integrated component of the full version of AutoCAD.
Autodesk now recommends using for all AutoLISP and Visual LISP development. It provides a much more robust, modern interface for writing and debugging code. How to Set It Up for Free: Solved: Visual Studio VS Code (VSCode) AutoLISP Extension
The classic IDE is already on your computer if you have AutoCAD installed. You can access it by typing VLISP or VLIDE into the command line.
Prior to the 2024 version, AutoLISP was not supported in LT. If you have AutoCAD LT 2024 or 2025 , you can now run LISP routines, though the full editor environment may still be limited compared to the standard version.
2. The Modern Choice: AutoCAD AutoLISP Extension for VS Code