Photoshop requires registry entries (Windows Registry) and DLL registrations. A true portable app writes nothing to the registry. Therefore, any "portable" Photoshop is either:

First, I should confirm that Photoshop isn't available on GitHub. That's correct. Adobe doesn't host their software there. They need to know that the official source is Adobe's website. Also, downloading Photoshop from unauthorized sources is risky. I should mention the risks of piracy and suggest legal options.

The only legitimate way to download and install Photoshop on Windows is through Adobe's authorized channels Adobe Creative Cloud

Adobe Systems does have an official GitHub presence ( github.com/AdobeDocs or github.com/Adobe-Consulting-Services ).