For Apps Analytics for an Android App or an iOS app, you can use the iOS SDK and Android SDK to track app sessions, screen views, events, goals, etc.

For a mobile website viewed within a mobile phone browser, when the browser executes Javascript, then Matomo will automatically work and track the site users. This will work for all kind of devices: iOs based devices such as iPhone and iPad, Android based phones or any other modern devices (running Palm Pre, Opera Mobile, Webkit, Mozilla Fennec, etc.).

For low-end mobile devices that use browsers which do not execute Javascript, you can manually record visits using the Matomo (Piwik) Tracking API. Learn more about the Matomo Tracking API. See also Does Matomo track visitors without Javascript?