How to revert to Android 9 from a Linux mobile installation?

Questions
1

Many of the currently available Linux mobile operating systems for Android devices (Ubuntu Touch, Droidian) begin their instructions for installation with:

Make sure that you have Android 9 installed on your device first.

There is no clear guidance on how to do that, especially not when you have already installed another Linux mobile os previously. Google has an online Android Flash Tool but this won’t recognise my device with Droidian already installed.

How can I flash Factory Android 9 onto a device that no longer has Android running on it?

Can anyone help?

2

Make sure the bootloader is unlocked and boot into fastboot mode on your device.

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3

For Pixel 3 XL:

Please note that these systems relying on this version still inherit many of those security issues accrued in the past 6+ years.

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4

Thank you. The Android Flash Tool recognises my device (over three different USB cables, different ports and in both Windows and in Linux) but once I start the install I always get ‘install failed’. I will try to learn about Fastboot.

5

Try using a USB 2.0 port

6

Try using a USB-A to USB-C instead of USB-C to USB-C.

7

I’ve tried it all. But maybe I’ve made an incorrect assumption about developer mode and usb debugging - do I still need to do those things when Droidian is already installed? I can’t 7x press on anything in Settings. When I power up and hold down volume it says bootloader is unlocked.

Under USB Settings the option is either File transfer OR Networking. I had assumed the networking option includes file transfer, but maybe I’ll try the other setting.

8

That screen with START is the screen you want to be on.
Volume down + power is the combo, be sure to let go of power after it turns on so you don’t accidentally select start.

Any settings in the OS (aside from the OEM unlocking toggle), have zero effect on the bootloader modes.

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