Fixed:

- Friendica\Content\BoundariesPager::renderFull(int $itemCount) must be
  compatible with Friendica\Content\Pager::renderFull(int $itemCount): string

src/Content/BoundariesPager.php

@@ -130,6 +130,9 @@ class BoundariesPager extends Pager
 		return Renderer::replaceMacros($tpl, ['pager' => $data]);
 	}
 
+	/**
+	 * Unsupported method, must be type-compatible
+	 */
 	public function renderFull(int $itemCount): string
 	{
 		throw new \BadMethodCallException();