The "recovery mode" is part of the boot loader, similar to the PC.
It can be used to repair and/or sideload the current OEM operating system.
Fastboot is more like a "bios".
Fastboot is a "command-line tool" with many more commands than just the one «flash».
But be warned, you can destroy your device, because similar to the bios of PCs, there are different fastboot properties depending on the device manufacturer.
@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!
Sorry have been away for a couple of months and only now finally got back to my OP6. Using the UB touch installer, I got Focul up and running. A couple of minor issues, the date and time (despite been set as automatic) seems to revert to manual on reboot. I get the Qualcom Crash Dump screen whenever I leave it charging....and on reboot get the Boot Loader is unlocked screen.
I have not had time to explore much more than this at the moment.
boot into android.
enable developer mode system>settings>about phone. Hit Build number a few times to enable developer mode.
Enter developer mode, enable USB/ADB debugging and OEM unlock
4)boot to the bootloader and in fastboot unlock the bootloader
5)boot back into Android and set it up again
6)enable developer options and USB debugging again
copy the downgrade ROM to the root of the device, ie, NOT in a folder
go to system updates and do a local update. It will reboot and you will be on Android 9.04.
enable developer options and USB/ADB debugging again
Unplug and plug the device back in again
Reboot to the bootloader and run TWRP recovery.
In Wipe and advanced wipe, ensure the DATA partition is EXT4
reboot to Android
14)USB/ADB debugging should be enabled
Start the UT installer and follow the instructions.
You have to install Android 9
IF you have installed LineageOS or any other version of Android it will fail to install, it has to be on Android 9
USE the Installer, the fastboot commands are only required to get the device ready for installing UT.
If the device boot loops, usually it is because your DATA partition is not EXT4 or your bootloader is the wrong version (one of the many reasons why you use Android 9).
So you need to get back to Android stock ROM and make sure it is Android 9.
I lack a lot of the understanding of whys and wherefores with the need to set it up in a certain way before installing UT as I am not a software engineer/coder or genius, but if you follow the instructions it should and usually works.
One rule for all of this is keep it simple (KIS), don't complicate things by overusing the command line.
@User100 Hey I realize this is old, but if you have not gotten it out of Qaulcomm Crash Dump mode yet the way to do it is getting the MSM tool. You can get the tool with Android 9.0 so that you can boot right into it. Here is the link to the MSM tool. Follow the guide you will find in there it works like a charm. I got the crash dump error twice trying to get it to 9.0.
If your phone is as finicky as mine when you start the process it will give you the sahara error... This is where you have to not listen to the instructions. Keep the phone plugged in and reboot with power + volume up, Then restart the phone with power volume up and you will see that the MSM tool will start the download again once it boots. You can let got of the buttons then and let it do its thing. If you have any questions feel free to reach out and I'll do what I can to help.
Side note.... Rollback option does not work with T-Mobile OnePlus phones.
@spaceman_spiff Not my fix, read about it on the forum or TELEports, but if it works, good. It is one of the tricks to remember for any sort of connectivity issue on UT, try switching airplane mode on and off first 🙂