Breeze to install

MrT10001

Got hold of a Oneplus 6. Running Android 11, so downgraded using OB25 build from here.
Unlock the device (open developer options by tapping build in about device until it states "you are now a developer", back to System, Developer options, enable OEM unlock and USB debugging). In a command prompt use ADB to reboot to bootloader and then use the fastboot command "fastboot oem unlock", then when done reboot the device and set Android up again. Set up developer options and USB debugging, set it file transfer and copy the OB25 file to the root of the device (i.e. not in a folder). Go to system update and check local update and tap the zip file. Allow it to do its thing and tap reboot when done. The set android up again and hey you are on Android 9!
Then just follow the UT installer.
Installed so easily, I thought it was a Nexus 4 (apart from the Halium splash). Less than an hour and it is up and running. Good device so far!

Moem

That's a nice, concise step-by-step!

MrT10001

@moem Thank you. Got hold of another one and it is just so easy to install to.

mw4jet

So, what about cell service? 4G, provider etc.?

I had a OnePlusOne that worked good, just couldn't use it because of the cell bands it needed were discontinued. I now have a Pixel 3a but it's 3G and that's a dud!

I am looking to use the phone on a GSM network in the US

MrT10001

@mw4jet Works fine for me on 4G. I am not in the US who seem hellbent on removing 3g and 4g bands, forgetting that Government agencies still use those bands and they are tried and tested technology. I remember when 3g arrived, so many issues, took a long time to iron the coverage out.

mw4jet

Thanks for the quick reply!! I would think 4G will be around for a while, so I may try and find a 6T.

Dunbrokin

@mrt10001 said in Breeze to install:

set it file transfer and copy the OB25 file to the root of the device (i.e. not in a folder)

.....could somebody flesh out the details of this sentence please. Perhaps named file in the zip to transfer...and how one finds the root of the device! Help much appreciated!

MrT10001

@dunbrokin Attach the device to your PC and make sure the USB mode is set to file transfer. The device should then show up in the File manager ( I used windows 11). On the device icon open it up and you should see the usual Android folders etc. Copy the OB25 zip file to the device so it sits next to the folders and is not in a folder, this is important and is basically the root of the device. Then go to system update, check local update and select the OB25 zip file and follow the instructions.

sven

In the xda-developers page, there are two files labelled OB25.

MrT10001

@sven There was only one labelled OB25 under the rollback ROMs to bring the OPO 6 back to Android 9. I will post the full title when I get a chance as I am not on my PC.

sven

@mrt10001 That description is unambiguous. Thanks.

MrT10001

@sven OB25 Rollback build:

OnePlus6Oxygen_22_OTA_054_all_1908302047_fulldowngrade_f019784c78234a67.zip

Dunbrokin

@mrt10001 Thank you so much for taking the time to explain all this. Much appreciated.

Dunbrokin

@dunbrokin
$ fastboot oem device-info
(bootloader) Verity mode: true
(bootloader) Device unlocked: true
(bootloader) Device critical unlocked: false
(bootloader) Charger screen enabled: true
(bootloader) enable_dm_verity: true
(bootloader) have_console: false
(bootloader) selinux_type: SELINUX_TYPE_INVALID
(bootloader) boot_mode: NORMAL_MODE
(bootloader) kmemleak_detect: false
(bootloader) force_training: 0
(bootloader) mount_tempfs: 0
(bootloader) op_abl_version: 0x0
(bootloader) cal_rebootcount: 0x31
OKAY [ 0.001s]
Finished. Total time: 0.001s

I cannot get adb to work....or give me any attached devices. Can only boot to recovery. No boot to stock or to twrp.

$ fastboot flash boot /home/monicap/ISOetc/lineage-20.0-20230124-recovery-enchilada.img
Sending 'boot_a' (65536 KB) OKAY [ 2.761s]
Writing 'boot_a' OKAY [ 0.522s]
Finished. Total time: 3.291s

But does not boot up on restart...only "the bootloader is unlocked....."screen.....Hmm! I think I must be bricked!!

Espionage724

@MrT10001 Thanks for the instructions! I was afraid I needed to mess with Msm from Windows or something but I wasn't aware of the flashable zips in that thread. I was running LineageOS 20 with F2FS unencrypted data and needed something to really work to revert all that fun to stock

I rebooted to bootloader, fastboot booted TWRP, formatted data and everything except vendor partition, rebooted back to bootloader and fastbooted TWRP again, adb pushed OnePlus6Oxygen_22_OTA_054_all_1908302047_fulldowngrade_f019784c78234a67.zip to /sdcard, flashed it from TWRP, rebooted to System, and was greeted with the stock boot animation and OxygenOS 9.

My host OS is Ubuntu 23.04 so I got the UBports .deb and installed it with apt, opened it up from the launcher, and chose 20.04/devel. Some stuff downloaded, I followed the UBports prompt to go to Recovery, and eventually Ubuntu Touch booted up!