I found with a new project, whether saved from another or started fresh: If you set the PWA to disabled true, and then, for the first time for this project, deploy it in any way - like start in desktop browser - causes a 404 for a missing pwa.js file.
If you go back to the project and enable PWA and redeploy, it creates the pwa.js file and it works fine as a pwa (or not if you’re not on a server). But it works as it should.
Then, if you disable PWA and try again, it works - because there is a pwa.js file that is loaded by the browser.
The pwa.js file should not be loaded by the browser in disabled pwa mode.
PS - running a project in non-pwa mode during your initial development cycle of a deploy every 15 seconds speeds up the process of testing significantly. That’s because you made a change and pwa noticed it, and delays the loading of the new page. Disable pwa, and the new pages load on “deploy”.