https://support.apple.com/guide/ipad/connect-external-devices-or-servers-ipad1c415e32/ipados
That looks promising. In practice, is the iPad going to copy any file I wish to access onto the iPad before launching an application to view/listen to the media? Or will those files remain only on the server?
Copy the files that you select, from a server (could be your computer), to your Files sub-directories that are appropriate for you.
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GoodSync is a possibility
https://www.goodsync.com/for-iphone-ipad-ios