Hi. I recently published my app on Flathub and have been steadily updating it to make it better.
With it you can download Music from Youtube and tag it to create a beautiful collection of local Music. Check it out: https://flathub.org/apps/net.fhannenheim.musicfetch


I’ve now tried a fresh install in a Fedora Workstation 43 VM with the language set to German and it worked.
You could try
rm .config/cosmic/net.fhannenheim.musicfetch -rfto reset the app and try again.