Cordova - Displaying local image files in a tag

I have a Cordova app (built on Ember.js, using the Corber addon) that I am currently only running on iOS, specifically the iOS simulator (iPhone 8, iOS v12), so it is using a WKWEBVIEW.

The app is using cordova's file plugins to download remote images and store them on the user's device, currently in the "Documents" (cordova.file.documentsDirectory), which works fine, and I've verified that the images do in fact exist there. However I can't figure out the correct URL/URI to use to display those images in the app via standard <img> tags.

Cordova's own documentation says to use the cdvfile:// protocol path (https://cordova.apache.org/docs/en/latest/reference/cordova-plugin-file/#cdvfile-protocol), but even with following the instructions there (adding the content-security meta tag to the index.html, the access rule to the config.xml, etc), it seems like WKWEBVIEW just flat out does not support this protocol, giving me "unsupported URL" errors in the console when I attempt to use it.

Other SO answers on the subject suggest using a normal URL path relative to the cordova app's web server URL, e.g. things like <img src="/Library/NoCloud/path-to-my/file.jpg"> but any path I try 404's.

This seems like such a simple/common use case, but I'm stumped.