The installonly_limit option is ok. Instead of having 3 kernel versions installed, you can have more.
The fact is that I’m unable to pin a specific kernel version. I’m unable to do that.
You can exclude a package from a DNF operation, but this doesn’t work with a specific version. If you exclude the kernel (--exclude=kernel) package, you can’t update it at all, and ok.
At the same time if you specify the specific version, I encountered these issues.
sudo dnf update kernel --exclude="kernel-5.1.4-300*"
Is ignored, dnf still wants to remove kernel-5.1.4-300
With
sudo dnf update kernel --exclude="kernel-5.1*"
Seems to work, but… since the newer kernel version is 5.1.12, dnf obviously says that there is Nothing to do (as it is excluded from the operation).
So, in other words, I’m unable to find a way to keep a very specific kernel version in place.