Tumbleweed install with secure boot failing

Hi, just got a new laptop with Windows 11 installed and I'm not supposed to remove Win 11 completely ;-) but want to install Tumbleweed in dual boot. Since apparently I'm installing only every few years it's always again "interesting". I downloaded a recent Tumbleweed snapshot and wrote it to a USB stick but I cannot boot from it as the system tells me that the secure boot signature is invalid. When trying to search for the issue I cannot find much. I found that Tumbleweed should be supporting secure boot completely and therefore I have no idea what might be wrong as apparently is meant to just work. Any pointers? Thanks, Wolfgang