Hello Roger
I have tried all but point 4 without success.
I think that I am going to have to rebuild the machine from scratch. Quite a mystery why this machine is stuck on this kernel.
Thank you for all your thoughts and time. It is much appreciated.
As a last hope, I uninstalled anything I could find for the 553 kernel and completely uninstalled NVIDIA. After reinstalling the latest 553 kernel and installing the Nvidia official drivers & cuda , I still get the same black screen selecting 553 but a full boot in 513.
I have just downloaded the latest dnf upgrade 4.18.0-553.8.1.el8_10.x86_64
and now 553 works.
I noticed that it installed linux-firmware-20240111-121.gitb that I had never seen before.
Maybe it was this that was missing.
All very strange.
Thank you for all your help.