You deploy to the cloud. The customer downloads a web page and that functions as a client that communicates with the python server. Just like how most programming is nowadays.

But if you want a customer to download an app, which is much more rare nowadays than you can do what Eve online does or iron mail. They deliver actual client side python apps. I don't know what they use internally or how they did it, but pyinstaller is one option you can use to build a python executable.