Comment # 6 on bug 1153847 from Ivo Lux

(In reply to Neil Rickert from comment #3)
> Unfortunately, there appears to be newer hardware that also doesn't support
> multi-signed shim.  We see that in forum posts.
> 
> Check https://en.opensuse.org/openSUSE:UEFI
> and scroll down to the heading 
> "Booting the Machine that supports only one signature with vendor provided
> Keys"
> 
> It suggests a workaround.  And you can use that workaround as a way of
> testing whether that is the problem.

I tried the suggested workaround. But nothing changed. Same behavior as before.