Now I'm on RUU mode (that seems to be fastboot, but with HTC flashing image on screen). Fastboot commands works. I managed to unlock it again via HTCUnlock so now I can flash unsigned files.
However, I can't get past the RUU mode: it doesn't boot on classic bootloader or in recovery.
I took some photos but my connection is very slow.
If I remember right there was a fastboot command to exit RUU mode, but couldn't find anything about that right now.
EDIT: managed to boot with "fastboot oem boot". But when I reboot, it comes back in RUU mode. Bootloader and fastboot still seems to be unavaliable :\