User error: "1" after migrate Drupal 9 > 10

There is likely a module or a theme that is not compatible with Drupal 10. Configure logging at /admin/config/development/logging to "All messages, with backtrace information" and provide the backtrace here.

Thank you @cilefen

User error: "1" is an invalid render array key in Drupal\Core\Render\Element::children() (line 98 of core/lib/Drupal/Core/Render/Element.php).
Drupal\Core\Render\Element::children(Array, 1) (Line: 416)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 458)
Drupal\Core\Render\Renderer->doRender(Array) (Line: 458)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 204)
Drupal\Core\Render\Renderer->render(Array) (Line: 474)
Drupal\Core\Template\TwigExtension->escapeFilter(Object, Array, 'html', NULL, 1) (Line: 90)
__TwigTemplate_42bdefe175c3c1544177838175fb81e0->doDisplay(Array, Array) (Line: 394)
Twig\Template->displayWithErrorHandling(Array, Array) (Line: 367)
Twig\Template->display(Array) (Line: 379)
Twig\Template->render(Array, Array) (Line: 40)
Twig\TemplateWrapper->render(Array) (Line: 53)
twig_render_template('core/themes/claro/templates/classy/layout/html.html.twig', Array) (Line: 372)
Drupal\Core\Theme\ThemeManager->render('html', Array) (Line: 445)
Drupal\Core\Render\Renderer->doRender(Array, ) (Line: 204)
Drupal\Core\Render\Renderer->render(Array) (Line: 158)
Drupal\Core\Render\MainContent\HtmlRenderer->Drupal\Core\Render\MainContent\{closure}() (Line: 592)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 159)
Drupal\Core\Render\MainContent\HtmlRenderer->renderResponse(Array, Object, Object) (Line: 90)
Drupal\Core\EventSubscriber\MainContentViewSubscriber->onViewRenderArray(Object, 'kernel.view', Object)
call_user_func(Array, Object, 'kernel.view', Object) (Line: 111)
Drupal\Component\EventDispatcher\ContainerAwareEventDispatcher->dispatch(Object, 'kernel.view') (Line: 186)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 76)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\StackedHttpKernel->handle(Object, 1, 1) (Line: 704)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)

Debug Drupal\Core\Render\Renderer->render to see what is passed to it.

@cilefen I don't know how to do that. Is there a tutorial page to help me do this debugging, please ?

@cilefen The php error is still present. Can you explain how to debug Drupal\Core\Render\Renderer ?

Debugging Drupal is very well documented online.

@cilefen
There are, you are right, quantities of tutorials on the web, I have seen it. But can you give me the right path to solve this php problem, and Debug Drupal\Core\Render\Renderer

Thanks

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