After 4-5 days self learning.
A little bit more detail instructions by me.
reboot phone to bootloader mode
fastboot update pa-ruby-alpha-1-oneplus8-20201122-image.zip
it will auto reboot when done
screen become mess can't see anything
this should show your device id
adb reboot bootloader (the recovery extract from payload of pa-ruby-alpha-2-oneplus8-20201221.zip)
fastboot flash recovery recovery.img
volume botton select boot to recovery
recovery will suggest factory reset do it
when finish it will auto reboot
reboot to 1st setup screen setting up rom
reboot to recovery Apply update from ADB
adb reboot recovery
volume botton select apply update from adb
press power to confirm
adb sideload pa-ruby-alpha-2-oneplus8-20201221.zip
wait the rom update
back to recovery screen press power to reboot
wait the rom reboot finished.
I hope this help.
This is the correct process.thx, okay, then propably i am just unable. i always flashed oos 11 on both slots, dont know that could be wrong...
i will give up for now, have to msm to get my device running again.
It was my fourth try to get this rom working
i loved this rom on my op6t