What would be the best way to track downloads by user? Is anybody familiar with a plugin (similar to EE's Link Vault) that tracks all downloads, by user?
You can track the number of times a file has been downloaded using the Asset Count plugin by Verbb.

As the readme shows, rather than linking directly to your files, you’d point the link to the plugin’s controller action:

&lt;a href="{{ actionUrl('asset-count/count', { id: file.id }) }}" target="_blank"&gt;&lt;/a&gt;