Symfonium offers many different ways to cache the media from your providers for offline usage.
You can edit your added media provider and configure auto sync, either the whole provider media or selected media librairies.
You can offline cache songs, albums, artists, genres, playlist … from the 3 dots menu then offline cache option. You can also enable automatic offline cache for genre / artists or playlist so that each time new content is added to those on your provider the new content is also automatically cached.
If you want to export the files to share with other applications, you can use the save to Downloads folder. But please note that those media won’t be usable by Symfonium in offline mode properly.
In advanced settings you can change the location of the stored files, and if your provider supports transcoding you can configure the quality to reduce the required storage space.