Comment by pxx

There are grounded duckheads for this purpose, e.g. https://amzn.to/4cnzuef (note out of stock. I guess your best bet is to use a UK duckhead, but half of those have a dummy ground...)

if you take the plug part from the brick you'll note that there's only two pins but the button-like thing is a ground

as noted in a sibling, the power adapter extension cable does plumb the ground through (https://www.apple.com/shop/product/mw2n3ll/a/power-adapter-e...)