Definitely Ubuntu, it’s the most user friendly for people coming from other OSes
I’d say Ubuntu again, or maybe Debian. You built up skill and learnt the distro so you want to use something you know for work. On your personal computer, try other ones. I personally picked Arch at this time (around 2012), which helped me “understand” how the OS works, rather than simply use it. I reinstalled it quite a few times and broke the system a lot.
Any distro with a simple package management system. My personal choice goes to crux, but it’s very barebones. NixOS or Gentoo would be fine too The point here is to learn how to build packages by building them yourself, and I feel like the “big” packages managers (apt, yum, dnf) are too complex for that. They also decorelate runtime libraries from headers files, which is a pain to work with as a développer IMO.
But it’s just my personal experience, many new distro popped up since then. Also for reference, I’ve been using Linux for 12 years now, and I run Crux on my desktop, Ubuntu at work, and OpenBSD on my servers.