Going further with development I had some issues with PurgeCSS as managed by webpack, so I switched to the Tailwind-integrated one.
On the latest versions in my branch you can see I commented everything about PurgeCSS in resources/assets/build/webpack.config.optimize.js and switched on the purge section in resources/assets/styles/tailwind.config.js.
I came across the same issue after I finished building the whole site and realized that I never tested production.
The error seems to be that the purge arguments are set relative to the tailwind config, while it should be relative to the root folder. I am not sure if this is only a Windows/WSL problem, though.
So this fixed it in tailwind.config.js:
There are still some issues with the __webpack_hmr error in the console when running yarn start: Failed to load resource: the server responded with a status of 404 (Not Found)
Those issues are very hard to track down. I already have tried to get it fixed.
Now the loaders have also changed, some were abandoned, some replace them.
A new branch is opened now that tries to use the latest packages (state 2021 end/2022):