OK, never mind, let’s close this as I seem to be unable to get myself understood.
Please just note that I do not have two kernels, and I don’t need two kernels. I have only one bootable kernel, which is the 5.14.21-150500.55.44. I also accept whatever package management system is chosen by the distribution developpers, I don’t challenge that at all neither.
I only say that as soon as I install NVidia and/or VirtualBox into OpenSUSE LEAP, some portions from older and already superseeded kernel versions get pulled into my system, and that does not seem to be the case anywhere else.
I think I got it and IIUC it’s simply the dependency of the Nvidia package that prevents some older kernel “parts” from being removed:
I am keeping my two kernels, but never mind, there’s the kernel-default-devel one step older: