Thanks for your suggestions!
I am using haiku-nightly-hrev51428-x86_64 and I cant get past Thinkpad´s own Boot menu. It does recognize the USB stick, but Haiku itself doesnt even start to boot.
I just tried it on another old lenovo netbook and it does not boot from the stick either. I followed the instructions on https://www.haiku-os.org/guides/installing/making_haiku_usb_stick/
Is there anything else I need to do before, like formatting the stick to a specific file system?