I noticed that the clipboard API is no longer working in Observable notebooks. Try it here: Copier / Mike Bostock | Observable
I’m using Chrome 93.0.4577.82 on macOS 11.6.
It looks like if Observable adds a clipboard-read; clipboard-write; to the allow property of the output iframes, that would fix it.
<iframe class="absolute bn " scrolling="no" sandbox="allow-same-origin allow-scripts allow-downloads allow-popups allow-forms allow-popups-to-escape-sandbox allow-top-navigation-by-user-activation" allow="geolocation; microphone; camera; midi; encrypted-media; autoplay; accelerometer; magnetometer; gyroscope; vr;" allowfullscreen="" src="https://mbostock.static.observableusercontent.com/worker/worker.35aeee9b01f0568adc6d0e093f7f3635b2b663b3edc544cc07da6375a006512a.html" style="height: 1271px; min-width: 100%; width: 0px;"></iframe>
