I think that making child themes for Block theme is the same as for Classic
Maybe you renamed theme folder or you removed file inc/block-styles.php from theme. Try to reinstall theme
I don’t know why you need it, because it’s a bit ugly, but, ok, I will enable it in next update
Please, note, that latest 5.9.3 version of wordpress disabled auto anchor generation for headings, so, TOC doesn’t work, we will force to enable this in next update of theme
