I feel like NixOS might be the only distro that could realistically handle all these use cases, but I’m a bit scared of the learning curve and the maintenance work it’d take to migrate everything over.

It’s a very steep learning curve, but I personally think it is worth it if what you want is to sync up all your various devices to a single common baseline configuration. I sought a single-distro solution for all of my systems for a long time and always ended up fragmenting them eventually because nothing I tried until NixOS was capable of handling such a diverse set of use cases in a way that would satisfy me.

I am similar to you, in that I regularly use a three server cluster, a gaming desktop, a multi-purpose personal laptop, and a work WSL instance on my work laptop. I still have some purpose-built distros where it makes sense; I use Proxmox for the actual server hosts themselves and then run NixOS VMs on them, along with running VMs for Home Assistant OS and TrueNAS (with the drives passed through, of course). All of these things I could do on raw NixOS (even Home Assistant is packaged in Nix, and there is a project to port Proxmox UI and tooling to NixOS) but I like the stability of the dedicated and battle-tested distros for critical infrastructure, especially for stuff whose configuration is very specific to a given task.

With NixOS, each other device has a consistent shared configuration and package set, they all get updated to the exact same versions thanks to flakes so everything works the same and as expected no matter where I am, and it’s all declaratively configured and documented in one spot. Spinning up a new system or rebuilding an existing system is as easy as pulling the config and changing a few relevant lines, and from there it effectively assembles itself from scratch to the exact state I want it to be in. There’s never any lingering packages or configuration cruft because the system is assembled from scratch every time it updates. Much of my home configuration is also managed, so aliases, environment variables, even vim configs are consistent across the board and set in one location.

The main downside is resource efficiency. Nix is designed to be reproducible and declarative, not fast or lean. It uses much more storage than a typical package manager, and packages are built with wide compatibility in mind so you often are leaving performance on the table from not using newer instruction sets like CachyOS. You can compile your own packages to fix that part, but that obviously takes a lot of spare processing power. I’ve been considering setting up my server cluster to do automatic building for me, but haven’t gotten around to it yet.