Incompatibility with x86-64-v2 means that CERN is running some older machines, over 15 years old:
https://en.wikipedia.org/wiki/X86-64#Microarchitecture_level...
For control systems, it’s perfectly reasonable to be using old stuff. Other than power consumption, you aren’t really losing anything, and I think that they famously have some other equipment there that consumes a touch more power than some old servers.
We run most things on Alma Linux, but there's also RedHat in the mix.
A good intersection of CERN and Gentoo is EESSI. They use CVMFS, which is a FUSE filesystem used for software distribution from CERN, and Gentoo as part of their software stack. See links below for more info:
Personally I have used Gentoo for many years, though never professionally. Its secure extensions were very well tested and documented back in the day, before SELinux pretty much took over. The kernel build system was terrific.
But never once did I consider setting compiler flags an important feature. The person who knows what flags are best used with an individual package, that -Os is more important than -O3 for this particular loop, is either the packager (who knows the system architecture) or the original developer (who wrote the code). Never the end user.
Debian is comparably a more mature system. The downside is perhaps that its packages are a bit more complex than they should be. Functionality-wise it can do anything you could wish for. But if you are a big institution with a lot of competent people in house, go right ahead. You can't possibly go wrong with a well tested system and the knowledge to improve the bits you need.
But, CERN may have some proprietary applications on those systems that force them to use a specific setup which is hard to replicate in other distros.
All this drama alienated many people who built their careers on RHEL-based systems, and created (either actual or perceived) instability in the RHEL ecosystem. And at the same time they started deprecating older hardware, some would say far too early. This is the “straw that broke the camel’s back”, as they said in the CERN presentation.
I was ready irritated by the title but then again, phoronix has been a joke site for at least a few years.