I think NixOS is a superb choice if you have the time and energy to invest in it. I’m currently using Guix System (a GNU fork of Nix) and I’m very very happy with it. Previously I’ve been on openSUSE Tumbleweed because I thought the most important thing for me was btrfs with an easy snapshot system. But then, one day, when I was writing ansible playbooks to configure my OS I realized that what I care most about is declarative configurations. Now I’ve completely stopped using ansible for my laptop/desktop, and just rely upon native Guix configuration. I love it.

I do still run MicroOS on all of my servers because it “just works” and I think transactional systems are great for servers. Recently, however, I’ve been thinking about trying out NixOS/Guix System as my server OS of choice, but we’ll see how that goes.

If you’re willing to put in the time, I think you’ll love NixOS.

Edit: Nix/Guix are also transactional.