You could do a lot more with this. Consider that the FF addon is a 'front-end': user options could include nightly updates (a must), audio only (mp3, flac, ogg, aac, opus, wav), streams: HLS->mp4, user url lists (it already does YT playlists).

Package yt-dlp 'full boat', with everything it needs: deno.exe, aria.exe, ffmpeg, ffprobe, all in it's own folder (all MIT or equiv). You already have a good start, take it the rest of the way.

Doesn't work says file not found

It works, but there's room for improvement. The red badges remain even after downloading.

To download, you need to right-click and select 'Download with yt-dlp' from the menu, as clicking the icon results in a "file not found" error.

To adjust parameters, you have to modify line 44 of the installed "yt_dlp_firefox" Python file. The save directory can be changed by editing line 34.

My settings:

Line 34:
DOWNLOADS = Path("M:\\New Shows")

Line 44:

["yt-dlp.exe", "--print-json", "--recode-video", "mp4", "--postprocessor-args", "FFmpegVideoRecode:-c:v h264", "--", url], # Use yt-dlp.exe on Windows

You have to be an IT pro to be able to make it work
In the official guides that you can find, it is difficult to understand the consistency or logic
Just an example from the guide "After installing the extension, clone this repository" - which "repository"?
Possibly a "windows_helper_installer folder" - but where is it - on my entire C drive I can't find one
Mayby you also have to install a "windows_helper" program - but from where - There is no zip file. And there i no better other explanation no matter how much you clicken through technical writings - Save yourself the time to spend on it
AND to the developer - Maybe your program is good, but if you can't make a bulletproof guide to how it works and how it should be installed, for a user who is not in the "context", then it fails