Lovelace: card chooser is empty

I ran into an issue, which I am not able to solve myself. In my Lovelace frontend GUI, when adding a new card, the “card chooser menu” is empty. See screenshot:

I tried this on multiple browser (incl. Incognito), but it does not seem to be a cache-issue.

Does anybody have tips on troubleshooting, etc.? :slight_smile: