Error 500 with API access to Joomla 4

You have configured an API access in Joomla 4, but you only get back "error 500" e.g. at https://<<yourdomain>>/api/index.php/v1/content/articles? If you have installed SP PageBuilder from JoomShaper, then deactivate this extension completely and also deactivate the associated Helix plug-in. In our experience, SP Page Builder blocks API access to some endpoints, e.g. articles.