by Hakan GERMAN on WordPress.org
InfoMon shows WordPress, PHP, database and server details in a clean admin page and a compact dashboard widget, with handy JSON export.

InfoMon admin page with KPI cards and sections
InfoMon is a lightweight system monitor for WordPress administrators. It provides an at-a-glance view of your environment:
/wp-json/infomon/v1/statusOnly administrators (users with manage_options) can view the data. All output is escaped.