Comment # 109 on bug 1173158 from Takashi Iwai

Note that the Tumbleweed Nvidia KMP doesn't sign modules because TW kernel has
no strict lock down against unsigned modules (it follows the current upstream
state).  The whole one-time cert is applied only to Leap 15.2 KMP.

Did you really install the latest Leap 15.2 KMP on the system that was already
Secure Boot enabled?  Check mokutils output, and try it again with the very
latest Nviidia KMP.

If you try again and still fail, please give the detailed log.  Otherwise it's
hard to analyze.