When inside a chart object, and selecting an element which contains text - I should see a Character section in the Properties deck of the sidebar; yet - it's not there.
The Axis content panel provides this. You can click on the hamburger button to open the dialog. In case of the legend or data labels it's not available at all. I support the request. At least we should give access to font name, size, and weight and perhaps also allow to change the color.