link: https://www.makeuseof.com/tag/website-desktop-mac-app/
You don’t really need a dedicated service to turn websites into standalone Mac apps. Your Mac’s Automator app will do just fine. Let’s see how to create a desktop app with it, which is just one way to use Automator with your browser.
To begin with, open Automator, select Application as your document type, and click on the Choose button. Now look for the action item Get Specified URLs and drag it to the right-hand panel. (You can use the search box to find the action faster.)
You’ll see that the default address in the panel is Apple’s homepage. Double-click on that address and replace it with the address of the website you want to turn into a desktop app.
Next, grab the Website Pop-up action and drop it onto the right-hand panel below the first action. Here you’ll find options to customize the look and feel of the desktop app.
Once you save this new Automator application, your desktop app is ready for launch.