Yes, just enabling a service or program is one line in nix but the module behind can do a lot of things (install the package, create and enable the systemd service file, install and setup any db if needed or other service dependencies, set some default settings…). For some service that would be quite the bash script.
Also theming in nix is very easy for the apps supported by Stylix.
You don’t need to add mcfly bash integration to your .bashrc manually. Remove it from home.packages and instead enable the home-manager module with programs.mcfly.enable = true;. That’s all you need to do, it has a enableBashIntegration setting that’s true by default. Same for atuin, programs.atuin.enable = true; is enough.
It’s an habit you have to learn when switching to nix, check first if there is a module for the program you want to install before resorting to home.packages or environment.systemPackages.
That’s all I can think about that’s unique to nix. The rest is about configuring your DE, WM, terminal, shell, apps… how you like it like in any other distro, just through nix instead.
I still wouldn’t call it an instance, that’s only data storage.
For migration it’s quite easy, there are different tools for it, Eurosky have one , PDS Moover is another, there are probably others.
As for finding people data over different PDS, an account is actually identified by a unique id, a DID. And there is another brick, another server, the PLC that store on which PDS is a DID stored.
It’s not “just bluesky”.
Mu is just a bluesky client. Eurosky is a PDS, the part that store user data in AT Proto ecosystem. The part that aggregates user data into a bluesky feed, the AppView, is still run by bluesky. Eurosky is planning on running one but it’s not done yet. But I would argue that this is less critical than the user data storage part.
AT Proto does not work like ActivityPub.
I remember reading somewhere that there was a legal component to the destruction too. If they destroy the original it’s a transformation form physical to digital but if they don’t it’s a copy which can be illegal.