Why when I deploy Filament on the server the data dropdown is empty?
Mixed Content means you are loading assets from HTTP when using HTTPS. Either your APP_URL is wrong or you need URL::forceScheme('https'); in your service provider
Question regarding docs / security: "This is not an issue with mass assignment."
I think it just adds to the first one. Filament uses mass assignment per default and this might feel unsafe. But only values with a field will be updated at all.