Also please note the web assets are pre-gzipped to allow smaller file size when being hosted on the Arduino device. This isn’t as common anymore but still exists to ensure the UI loads when served off the microcontroller (smaller file size to transfer).
Because of this, you need to add the correct headers to the HTTP server for file types “cgz” and “jgz” which are just the CSS and JS files gzipped, respectively. Alternatively, you may decompress these files and it should work fine.
This is described here: https://opensprinkler.freshdesk.com/support/solutions/articles/5000164006-using-a-different-server-for-ui-assets