Hi Kate and happy Friday!
You are spot on: we have prevented folks from being able to directly upload files to your server as a security measure. There is no easy way to determine the safety of a media file being uploaded and allowing files to be uploaded (especially on a public submission form) would leave a lot of sites vulnerable.
I am not aware of a workaround that would allow specific people to upload files instead of others. I suppose one way to do it would be to create a custom field for the Events post type using another plugin like Advanced Custom Fields, adding that to the Community Events submission form template, and then making it visible only to specific user types. That would take some exploration for sure in addition to custom development, but might be worth looking into.
Sorry I don’t have a concrete solution for you here, but does this at least help answer your question? Please let me know.
Thanks!
Geoff