I would say NixOS, where it is trivial to switch across releases, run software from different releases, and perform rollbacks.

I have been running NixOS on several servers for more than a decade. No reinstalling, upgrading, or any breaks whatsoever.

I've only been running NixOS (in any serious capacity) for three years, but I have installed it on every computer that I am allowed to install it on now.

It has been the most headache-free Linux I've used, simply because I'm less scared to play with and fix stuff. The fact that rollbacks are trivial and snapshots are automatic, and since everything is declarative in a text file anyway, I am way braver. If I do something like screw up the video driver, or the wifi driver or make it so the system doesn't boot anymore, all I need to do is reboot and choose a previous generation.

I run nixOS as well on my home infrastructure (gateway/firewall, a couple of internal servers).

But I have had, uh, non-trivial breakages happen also when I upgrade the system itself to the next yearly release. Non-bootable kernel kind of breakages.

But I will give you that I can just boot from the generation before the upgrade, and it works again. So there's that :)