If you don't need the GPIO then buy a small form factor office PC like a Dell Optiplex Micro or a Lenovo/HP equivalent. They cost about the same on the used market, are more performant without the ARM headache and use only marginally more power (maybe 5-10w more at idle).
refreeze
Ubuntu -> Arch -> Debian (stable) -> Fedora Silverblue -> NixOS
I'm curious, why do you use LVM with BTRFS and not just use BTRFS built in subvolumes?
btrfs snapshots are still useful on immutable distros to recover accidentally deleted data.
You will hate Ansible if you are coming from Nix. I went the other way and Nix is 1000x cleaner.
Being able to actually reverse changes is trivial in Nix, but can be a headache in Ansible. Not to mention the advantages of writing in an actual language and not yaml full of template hacks. I personally don't see much future for tools like Ansible, there is considerable inertia working in its favor right now and it is absolutely true that it is widely used, but the future of configuration management is for sure more aligned with how Nix works.
Similar to my scheme:
laptop = "laptop"
nas = "nas"
router = "router"
Then if there are more than one in each category I use nas-0, nas-1, etc.
I have used all three! I started with Server then went to CoreOS running Kubernetes and settled on NixOS which I have been very happy with for about a year now. I run about 25-30 services all using built in modules.
Regarding security, if you are using well crafted modules on NixOS, there should be good systemd hardening in place. That being said there is no reason you can't just use containers on NixOS.
I also find deploying NixOS far superior to butane/ignition used by CoreOS/Fedora. I use nixos-anywhere and can deploy my entire server in a few minutes without manual intervention.
I have been reading about this since the news broke and still can't fully wrap my head around how it works. What an impressive level of sophistication.
HP = Has Problems
It's a real shame that Nautilus doesn't have a built in split view, I always love that when I try Dolphin.
As of the latest release (21), you can simply install microG on regular LOS and no longer need to install LineageOS for microG since it now includes the necessary signature spoofing support.