Numbering channel downloads

So the following can be used to download items from a playlist in numbered order (so I can sort by number):

yt-dlp -f bestvideo+bestaudio --merge-output-format mp4 -o "./<FOLDER NAME>/%(playlist_index)s [%(title)s].%(ext)s" <PLAYLIST LINK>

But as far as I can tell, I can't do the same when downloading a channel. The closest I could find is using upload date:

yt-dlp -f bestvideo+bestaudio --merge-output-format mp4 -o "./<FOLDER NAME>/%(upload_date)s - %(title)s.%(ext)s" <CHANNEL LINK>

Anyone know how I can replace upload date with just a number/ordering?