Plugins can be installed by uploading the zip file to Playground. The activate button post-install doesn't work.

Unsafe attempt to initiate navigation for frame with URL 'http://localhost:5400/remote.html?v=6f6bc49fac76f86a78a3dbf85c7c44b9cd4f7648&storage=temporary&progressbar=true&php=8.0&wp=6.3' from frame with URL 'http://localhost:5400/scope:0.1738060502738601/wp-admin/update.php?action=upload-plugin'. The frame attempting navigation is sandboxed, and is therefore disallowed from navigating its ancestors.