I am creating a new setup wizard from scratch. I wanted to know how do I change the OS language programmatically or setup the wifi connection. I don't find many sources regarding this subject. Specially if I want to do it without using Google services. More than a specific answer, I would like to know what is the best source for this kind of project. Thank you! :)
The setup wizard in the Android devices is usually made use of, by a home (launcher app) with a higher priority for the first launch. Once the tasks like WiFi and Language setup are complete, the app is disabled and the launcher app is started. Ofcourse, this needs to be a system app.
You can take LineageOS SetupWizard as a reference point. (There might be dependencies on Lineage's own framework/sdk but for reference APIs, you can start with this).
Ref: https://github.com/LineageOS/android_packages_apps_SetupWizard
Take a note at these key components
android.intent.action.DEVICE_INITIALIZATION_WIZARD.All these links should be sufficient to answer your question I believe.