Google was kind enough to give the AI overview a stable CSS class name (to date), so this userscript has been effective at hiding it for me:
window.addEventListener('load', function() {
var things = this.document.getElementsByClassName('M8OgIe');
for (var thing of things) {
thing.style.display = 'none';
}
}, false);
window.addEventListener('load', function() { var things = this.document.getElementsByClassName('M8OgIe'); for (var thing of things) { thing.style.display = 'none'; } }, false);