There is something seriously wrong with WordPress when a core update causes sites to require an additional plugin to resolve JavaScript issues which were not apparent in the previous version.

I experienced this problem yesterday. I first noticed it when Media Library did not display any media. All that was displayed was the Add New button.

I discovered that various problem could occur in the Dashboard.
Appearance > Themes > Add New stopped working. And so did the Theme details button. I discovered these problems when the only plugins I had active were Gutenberg 8.7.1 and WordPress SEO 14.7. Deactivating either of them would resolve the issue.

Installing the Enable jQuery Migrate Helper plugin does resolve the issues. But I shouldn't have had to have done this. Where were the "deprecated" messages of yesteryear?

BTW: The active theme was Twenty Nineteen v1.6