On the help page (/admin/help/styleguide) there are two warning messages.
Warning: strpos() expects parameter 1 to be string, object given in Drupal\Component\Utility\UrlHelper::stripDangerousProtocols()
Warning: htmlspecialchars() expects parameter 1 to be string, object given in Drupal\Component\Utility\Html::escape()
Visit the help page of the style guide module: /admin/help/styleguide
The problem can be found in the styleguide.module file's styleguide_help function.
The URL object needs to be converted to string.
2.0
Code
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
I verified the bug. The help page at /admin/help/styleguide crashes with an error about a Url object being passed instead of a string. The solution in the MR fixes the page and there are no more errors showing up in the site log. It's a simple bug with an easy fix. This is RTBC.