Preloader for flexdashboard

I've run with some issues with a flexdashboard that is loading for a longer period of time.

I'd like to add a preloader there, but it doesn't seem to work with any of the combinations (e.g. by using before_body, after_body, in_header, css, etc.); also not with including it within the code with different tags.

Would you have any suggestions on how to approach this?

It seems like the issue is not that the preloader doesn't load; but it loads only when the dashboard itself has been loaded, making its point useless.

Would provide a reproducible example, however cannot easily reproduce the problem due to several different charts & data sources that are being used for the dashboard.

However, I would add any of the preloaders available here. I've tested them both with html_output and flex_dashboard and they work fine within rmarkdown, just cannot get them to serve the purpose.

Would the shiny css loaders or similar work with flex dashboard?

Thanks! However, as far as I could see these are only loaders for charts and objects within the dashboard.

I've checked and I can already create such loaders that function well once the dashboard starts (e.g. with ajax starts), but I had no luck with actual preloaders.

would something like this work?

When I deal with this type of issue in shiny I try and get the app to load as fast as possible, even it means asking the user to click a button to load the data. No user has complained yet, and avoids the very awkward loading problem in live demos.