Query Monitor complains about a missing JS script called “wp-polyfill”. This one leads in several settings of eg. the Payment Plugins for Paypal to a weird view, where several settings that are probably supposed to appear in several tabs, are appearing in the same form.
Example:
Apparently its a JS polyfill that was added in WP 5.8, to replace “outdated” / unused things and add support for older browsers.
The issue appears in the RC1 and the current nightly builds, too.
cu, w0lf.