I want to convert my archived .flac library to .ogg for daily use. Using

find ./ -iname '*.flac' -print0 | xargs -0 -n1 oggenc -q6 

on the root music folder and then deleting every .flac (having copies of them in archive) seems straight forward, after trying it with one file it worked and all of the tags were transfered, too, except for one: Embedded album art!
I always prefer emedded covers over folder images, since I have some albums with varying covers.

One possible solution is discussed here, but the script only works if the image is already extracted: Embed album art in OGG through command line in linux

One possible solution I thought about was extracting album art from every song (not every song has one, though, and some even 2 or 3!), temporarily saving it and then using the script to include it into the finished .ogg.
But then I want to increase the number of processes xargs runs simultaniously to save time, so the temp images need to have a distinct name.

Is there a (linux) program that knows how to handle this? Or is there a finished script floating around somewhere?

It would be nice if oggenc supported adding embedded coverart and it really is a shame, since these two formats should (in theory) share the same tag format.

Edit: 15 days and noone even tries to answer. It’s funny, most of my questions don’t get answered. Too hard? Wrong SE site?