There are Android Apps for Guitar and other instruments also. Plus there are links to many Free Modules at, music slide rule dot com, https://musicsliderule.com/index.html
The Free online Modules may have adverts, but the Apps do not have any advertising. You do not need to be online unless you use an external link to the free modules, You may see adverts from the online content only.
The Apps are best viewed on Tablets or Large Screen Smart Phones. For beginners it is recommended to start with the App The Magic Circle of Fifths Guitar 1 for Beginners and study the section on Beginners Easy Practical Theory.
The apps at, apps for guitar dot com, https://appsforguitar.com do not play music, they are not intended for entertainment, they are intended as a visual aid and an invaluable resource of information for musicians, teachers, students, and the self taught. As many people are, eye minded, the apps are intended as a visual aid for quickly and easily finding chords, scales, modes and patterns, to enable discovering information for themselves.
You do not need to read music to use the apps, and there are no adverts in the app.