The Global Styles missing

I am working on my first block-based theme, and trying to leverage theme.json as much as possible.

I would like to allow client to change the the fonts, colors and other variations defined in the theme.json globally, for the whole site, and in the tutorials over the net I saw this can be done in the Global Styles menu.

But, I don't see Global Styles menu in any of the block-based WP sites I have access to, including the Gutenberg demo site.

What am I missing? Is Global Styles feature deprecated? If not, how can I find / enable it?