Ok, tried the
fastboot boot OrangeFox-R12.1-Unofficial-OPKONA-OOS13-V14.img
method on OnePlus 8 Pro EU with crDroid 9 (A13, F.15 firmware) - and it boot to recovery!
But - there is always one
- it provides decryption of /data with PIN or Password only.
As I'm using pattern I'd always have to change unlock method to PIN before entering Recovery.
Wrote to both slots a & b permanently with:
fastboot flash recovery_a OrangeFox-R12.1-Unofficial-OPKONA-OOS13-V14.img
fastboot flash recovery_b OrangeFox-R12.1-Unofficial-OPKONA-OOS13-V14.img
EDIT: Ja well, hit that roadblock... crDroid9 seems NOT to use FBEv2...
decrypt ended with signal: 6
/data partition seems to be f2fs...