I have an RCA Galileo Pro 11" running Android 6.0 Marshmallow. In the recovery menu, I have the option to install an update from the SD card or over ADB, either without rooting. I'd like to run a newer version of Android, if possible.
What would be the best way to apply the update, and what would be the best package to use? I am not willing to root my device.
You can only install updates that are explicitly created to run on your device. Those update files are usually automatically downloaded by your device over Wifi and then automatically installed using the mechanism you already discovered.
Usually for cheap device like yours the manufacturer never releases any major updates (updates that upgrade the device to a new major version of Android). Therefore if no updates are available you can't install any updates.
The only option would be to root your device and install a custom ROM if available. However this step is risky as there is the chance to brick your device and you have to trust the author(s) of the custom ROM.
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