Best Sites Are Not Optimised for Any Browser, They Work Equally Well With All of Them
Red Hat (IBM) is making rubbish sites
As far as I can tell, every browser that I know of (even NetSurf and Lynx) is compatible with this site since dumping WordPress. Browsers that block (or do not run JS) won't miss anything, however there are advanced elements in CSS which some browsers would not apply/render. It's true, albeit there too there's graceful fallback.
It's shocking that the same companies (I'm looking at you, IBM) that insist that they care about blind or partially-blind people (when proven they don't, based on Wayland force-feeding) are making Web sites that don't work even in Falkon (which is technically a decent browser):
All the pages began looking like this earlier this year. They basically broke their own site and didn't bother ameliorating/fixing it. It says a lot about how much Red Hat (or IBM) values accessibility, usability etc. █