Unable to redirect `file:///` requests

Question

I am trying to override file:/// URLs, whether pointing to files or directories, to let my extension show its own file browser for directory views and also potentially allow editing of individual files for files.

I made the following attempt, but the listener was never triggered for either files or folders:

browser.webRequest.onBeforeRequest.addListener((details) => {
    const {documentUrl, originUrl, type, requestBody, url} = details;
    if ((/^file:/).test(originUrl)) {
        return {
            redirectUrl: browser.extension.getURL('filebrowser/index.html') + '?abc=1'
        };
    }
}, {
    urls: ['file:///*/*']
}, ['blocking']);

I did add the "file:///*/*" permission to the manifest ("<all_urls>" also didn't work) (and I added "web_accessible_resources" for the redirect, but that was never even reached).

I am guessing this may be because of https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/API/webRequest/RequestFilter#Type , where it states that only requests made using HTTP/HTTPS will work for events despite file patterns supporting other protocols. However, onHeadersReceived does seem to receive at least the file:/// file requests (though not directory requests) even though onBeforeRequest which is needed for redirects, does not.

Can anyone confirm whether there are any workarounds?