I ended up just building a box after looking for the perfect NAS and finding it didn’t exist. The software is usually just crap or the hardware is underwhelming. Got a Node 804 case to slap in plenty of HDD space. Running NixOS so I’m in control of the software. In retrospect I wish I had gotten a rackmount type case. Tossed in an Arc GPU for better transcoding shortly after the initial setup.

Major desktop environments are KDE as you mentioned and Gnome.

Arch wiki is a good resource even if not running arch. You may want to look into their dotfiles page to back up your settings: https://wiki.archlinux.org/title/Dotfiles.

NixOS ended up being my distro of choice for reproducible installs but it has a high learning curve and poor documentation so I wouldn’t recommend to start with. That said you can still use Nix on other distros with home manager to manage dotfiles and install non-system apps.

Distros just pick the default things to install. You can always use the package manager to install something else like a better file manager.

A lot of choices are simply subjective so its hard to recommend any one distro. Mint is close to windows, based on Ubuntu and uses Gnome. Ubuntu based on Debian I find to be user friendly. Not used a Fedora based distro in ages but there is also Silverblue I’ve heard mentioned positively.

Distros like Arch and NixOS are more design your own system setups. Pick what you want. I used arch for a bit, but got annoyed at keeping all my systems in sync. Had a huge wiki of all the tweaks I made. Then scripts to automate some of it. I started looking at automation tooling like ansible when I found nix.