single post without title

I want to hide the title in a single post. That should actually be possible under "Options/Hide Title".
But it doesn't work. Where is the problem?
This works with other templates. Can you help me?

Hello,

Is this Joomla or WordPress?

Thanks,
Milos

I have a Joomla 4 installation!

And where are you disabling titles on this template?

The title for an article can be disabled by editing the article’s menu item (if it has one - this has priority) or in the article’s settings.

Best regards,
Milos