Developer mode has never been required on Android. App sources are managed by regular settings (Android 8+). Before that, there was a single switch for all non-Play-Store sources.
1. User downloads an .apk using a browser
2. User tries to open it
3. Android prompts the user to allow the browser as a trusted source
1. User downloads an .apk using a browser
2. User tries to open it
3. Android prompts the user to allow the browser as a trusted source
4. User agrees by flipping a switch
5. Installation resumes
6. User enjoys the app
https://developer.android.com/distribute/marketing-tools/alt...
https://android.gadgethacks.com/how-to/android-101-sideload-...