Nothing wrong with Ubuntu, but its a ready to use easy to install grandma Linux distro. If someone is an IT cyber security expert nerds would expect an OS like qubes, Debian or arch.

see your point 😅 but still, being cyber expert doesn't mean that you must compile your own Linux kernel and write your very own drivers for the hardware, or else you're a normie 😉

Not really. There are many really good hackers with a Mac and I even know a few that run (and hack) Windows. Ubuntu is good, you need wide tooling for hacking. Also, we don't use "cyber security expert", no one who is one would use this phrase to describe themselves, ever :). If their business card says "cyber security expert", the only answer to that is "good for you, bye" :)