Is it possible to restrict/convert the image file-type of a thumbnail when using --embed-thumbnail ?

[adanvdo]

This is really a problem in yt-dlp, but I was curious if we might be able to add support for either restricting the file-type of the thumbnail used when using --embed-thumbnail, or converting an available thumbnail to a specific file-type before it is embedded?

The problem is that when you download OPUS audio from a YT url the thumbnails are in webp format which cannot be embedded. I do not know if the ThumbnailData contains multiple file-types we can choose from or not. If it doesnt, the next thing I can think of is to convert the existing Thumbnail to JPG.