How do I include Matomo reports within an Iframe?
To include your Matomo Analytics reports in your website or app or dashboard, using an iframe, we recommend you use the « Widgets » feature (Widgetize).
Another option (not recommended) is to embed the whole Matomo UI in an iframe. For security reasons, including Matomo (Piwik) in an iframe first require you make small change to your config/config.ini.php
file: see this FAQ.