Apparently this is a new bug introduced today. It occurs with the inclusion of the Knowledge Centre feature, which has just appeared this morning for us.

It occurs when Admin Usage Tracking is enabled in Admin Configuration. The best workaround at the moment is to simply set Admin Usage Tracking to no in the configs.

I've raised an issue at Github for this: https://github.com/magento/magento2/issues/37618

Apparently this is a new bug introduced today. It occurs with the inclusion of the Knowledge Centre feature, which has just appeared this morning for us. It is due to an Adobe change in an externally loaded JS file.

It occurs when Admin Usage Tracking is enabled in Admin Configuration. The best workaround at the moment is to simply set Admin Usage Tracking to No in the configs.

I've raised an issue at Github for this where other users are reporting the same. https://github.com/magento/magento2/issues/37618