After a few hours of unsuccessful attempts to configure youtube-dl I realized that it was replaced with yt-dlp in v8.18, and config files should be named/structured as for yt-dlp.
Please, change the name of youtube-dl to yt-dlp in dietpi-software menu (what can break someones’ scripts), or specify that config files for youtube-dl from dietpi-software should be made as for yt-dlp in Quick start for youtube-dl.
Thank you.