[OnePlus 6 ROMs, Kernels, Recoveries, & Other Devel] egandt:
Here are my steps to go from OB2->OB3 and Liquidmix 9/16->9/22

Here are my steps to go from OB2->OB3 and Liquidmix 9/16->9/22, I'm sure you can remove some but I wanted to be complete so include a few that are likely unnecessary, for most people as well. Also should work for any future upgrade including an Oxygen version change, or coming to Liquidmix for the first time from Oxygen (Oreo or Pie)

I'm using OB3 factory ZIP, 9/22 build of Liquidmix, Magisk 17.2 beta and Bluespark's TWRP.

Warning: If you have an encrypted DATA partition (AKA: asks to decrypt on entering TWRP) you will loss all your DATA, settings programs ...

So BACKUP Internal storage before you begin

. I hate Data encryption as a result, so I will disable it below!

Steps (including extras just to be safe):

Reboot into twrp

-- check the Slot if the Current is A after flashing it will be B (if B then A)

Flash OB3

flash twrp

-- check the boot partition is not reversed

reboot back to twrp

Flash OB3 again

-- We now have OB3+twrp on Slot A, and Slot B

-- check teh current Slot to be safe

flash liquidmix (9/22 in this case)

flash twrp

-- Again verify that the Boot Slot is changing (to be safe)

reboot back to twrp

flash liquidmix (9/22 in this case)

flash twrp

-- I Like to be on slot A (for historical reasons, so I make sure I am on Slot A, if not I select Slot A and reboot to TWRP again)

reboot back to twrp

-- We now have Liquidmix+twrp on Slot A and B, and am booting from Slot A

flash gapps

flash universal-dm-verity-forceencrypt (if you do not want to encrypt and am flashing magisk)

flash magisk (as desired)

Wipe Cache/Dalvik

-- If your DATA was encrypted (had to enter a pattern to decrypt Data for TWRP on startup, now is the time to format it, otherwise the boot will fail). Wipe->Format Data (everything on internal storage, so everything is now gone).

reboot to System (This should now be booting slot A Liquidmix)

First ensure you see the Liquidmix boot animation if not something has gone wrong, review the process. If you formatted DATA beware you have no zips on the phone any longer use "adb push <file> /sdcard/" to upload the required zip files again, if something goes wrong.

Post steps:

Complete first boot setup including add in a finger print (this is important, as we need to verify Data encryption)

Verify Root if installed (should pass safetynet with 17.2 beta)

Advanced reboot (boots to TWRP aka recovery).

--You should not be asked to decrypt Data at this point, if you are then you need to wipe the data partition and re-flash

universal-dm-verity-forceencrypt+magic as you will be unable to update to the next liquidmix cleanly otherwise.

Reboot System (should boot very fast now as nothing is installed and everything is cached)

Finally I suggest a TWRP backup at this point to be safe. I suggest backing up (Boot/System/Data), as I've found you can not safely restore any of the others (so why waste space).

Start using your phone, in the knowledge that you should be able to upgrade to the next Liquidmix version without losing any data.

Note: To restore internal storage I suggest using adb push as it is faster and less prone to failing that using file transfer, to do so use "adb.exe push <directory> /storage/emulated/0"

I hope this is of help to others,

ERIC