due to personal reasons i can no longer maintain this (or any other) device.
i'm not gonna bother everyone why this is but it's temporary only i don't know how long.
i hope we find someone to replace me while i'm absent.
In the meanwhile keep enjoying crDroid and we'll meet again
Ok i understand now the slot a/b procedure.
When you restore the stock rom with MsmDownloadTool V4.0.exe, the msm tool will flash the rom only on one slot.
After the restore you have to unlock the bootloader (have wlan connection and check oem unlock on developert settings).
After that you reboot to fastboot and put in the cmd "fastboot --set-active=a", so now youre on slot a.
Before you flash the fastboot update, you must check which LPDDR variant you have. LPDDR4x or LPDDR5.
You can ceck this that with the command "adb shell getprop ro.boot.ddr_type", 0=LPDDR4x or 1=LPDDR5.
The wrong setting can HARDBRICK your device!
Now you can flash with "OnePlus8TOxygen_15.E.28_OTA_0280_all_2107310147_ddcd_Fastboot-ROM" with "flash-all.bat" which is inside the folder, the update will flash on the active slot a.
After that you change to slot b, "fastboot --set-active=b". and repeat the "flash-all.bat" progress.
Copy it in your root dir on sd card.
Go to settings and choose local update, install it and reboot.
the update will be flashed on the non active slot a (before we was on b).
you can check this in fastboot with "fastboot getvar all".
Search for "(bootloader) current-slot:a"
Reboot and do the same thing with the local update and the update will be flashed on the non active slot b,
Now we are back on slot b and the latest firmware stock rom is active on both slots a and b.
Check it again with "fastboot getvar all", you will the see "(bootloader) current-slot:b".
So now we're ready to flash the "recovery.img" recovery.
reboot to recovery, make a factory reset.
Go to apply update and flash with "adb sideload crDroidAndroid-12.1-20220403-kebab-v8.3.zip".
At error 21, signature failed, tap "install anyway".
reboot to recovery and do the same for your gapps and magisk.
Take magisk.23.2 and upgrade via magisk-manager, tha latest package will failed to flash.
Its for new users, they have the same problems to understand whats going on with these A/B Systems.