just as an information:

i could remedy my mistake (not updating to the correct version before flashing with linux) by getting some inspiration from the previous build and install instructions (https://sailfishos.org/wiki/Sailfish...y_period.21.29)

- i edited the flash script, commenting the part with oem flash:

sed -i 's/echo "Flashing oem partition.."/echo "oem partition is populated manually through recovery"/' flash.sh
sed -i 's/$FLASHCMD oem $BLOBS/#$FLASHCMD oem $BLOBS/' flash.sh

- then copied the *loire.img files by hand to the appropriate partition:

- flashed the phone with the sony blobs:

fastboot flash system *_loire.img

- did a boot into recovery image:

sudo fastboot boot hybris-recovery.img

- telneted into the phone in the rescue boot.
- and copied files according to instructions here

- afterwards rebooted the phone into fastboot mode again
- and flashed again with the modified flash.sh
- and that worked.

my phone now boots into sailfish x. too late to check functions now.

that'll teach me (again) to better respect instructions before doing stuff.

thanks for the hints!