How can I set default font size for quote blocks?

Hi, I’m using WordPress 6.4.2, Twenty Twenty-Four (child) theme.

When adding a quote block in a post, the default text size is huge – larger than the surrounding context. In the style settings for the quote block the typography does not appear to be set (none of the options – S/M/L/XL/XXL – are selected). When I click “L” the font size remains the same (meaning, at least to me, that the default size is “L” even though the “L” does not appear to be selected). “M” is much better.

I know how to change that one by one, but I have many quotes. How can I make the default text size “M” for all quote blocks (i.e. “M” is always selected by default)? (preferably WITHOUT A PLUGIN). I don’t mind CSS, but I text-searched the entire WordPress install (including theme files) for “wp-block-quote” (the CSS class that WP assigns to these quote blocks) and can’t find it ANYWHERE.