That command is for Xperia X, Xperia XA2 and Xperia 10. But you have an Xperia 10 II, haven’t you?
The commands should be:
sudo fastboot flash boot_a hybris-recovery.img
sudo fastboot flash boot_b hybris-recovery.img
as in this chapter.
sorry - that was a typo - the phone is a Xperia 10 - I4113.
I replaced it with a 10iii now - but may have a look if maybe i used a wrong tutorial or similar when i have some time.
thx for the input