Xperia Z3 bootloop after TWRP Xperia Z3 D6633

I followed the very many tutorials (pick any on google) saying to flash (in fastboot) the file bootZ3monxtest01.img

fastboot flash boot bootZ3monxtest01.img


Now I have a bootloop around the sony logo.

No system, only recovery (TWRP) available

I can also reflash the whole system through Sony's Flashtool, but it kills the point, as a custom working recovery is required for later rooting

Obs. 1:
Needless to say that the "usual" is to flash recovery onto recovery partition. I tried that. Nothing happened

Obs. 2:
KingRoot rooting method worked, but I fail miserably to replace it by SuperSU

Obs. 3:
It's my third attempt

:(
I found another method (buried lightyears deep on the net):

http://squidstech.com/2016/11/27/root-z3-23-5-a-1-291-d6603-d6633-d6653/

It flashes the recovery via ADB
(requires a prior kernel change, though, that can be restored after)