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Listing tables merely requires the SELECT privilege in MySQL / MariaDB. This is the same privilege that's required to read content from these tables, an operation that's necessary for Joomla to run at all. Therefore, we can conclude the problem is not database user privileges.

If there was a PHP error happening, such as running out of memory due to a large number of tables and an insufficient memory_limit, we'd be seeing either a server error page or a completely blank page. You see the rest of Joomla's interface, therefore it's not a PHP error either.

These two deductions are very important because they eliminate two of three possible problems which could lead to something like what you describe. Which leaves us with the third option: a JavaScript issue. Open your browser's dev tools (usually hitting F12 on Windows, or CMD-SHIFT-I on macOS) before clicking on Exclude Database Tables. Go to the Console tab. Clear it. Then click on the Exclude Database Tables. Do you see any error messages there?

This error is not coming from our software. It appears to be coming from a colour picker. I have the feeling you have a browser extension which is injecting some JavaScript that throws unhandled errors. Any error thrown by any script on the page immediately kills all JavaScript execution on the page.

You can confirm that JS crashed on the page very easily. Just click on an empty are on the page and press the J key followed by the X key within 2 seconds. Normally, this pops up the Joomla Keyboard Shortcuts. If you get nothing, yeah, JavaScript execution on the page died because the third party JavaScript threw an error.