Success at last! It is apparently very import to unlock at "latest android". I unlocked at Android 6.
I installed twrp like this:
sudo fastboot flash boot boot.img
It will then always boot into twrp, but I didn't manage to flashing it to the recovery area to work.
Once booted into twrp, I had to format system, data & cache since the phone got encrypted by default.
Btw, ip configurtion from console:
sudo ip addr add 10.15.19.1/24 dev -your device-
For those of us that don't have a fancy GUI to help you with.
ubports on xperia x feels a bit sluggish compared to the nexus 5. A look at top, shows that unity8 consumes quite a lot of cpu when doing some ui interaction. I suspect no hw acceleration enabled?
edit: Some language corrections.