Maybe I’ll write something in the future

It was not too hard if you are already familiar with Nix. The features supported (and the custom Linux kernel) can be found in surface-linux. For NixOS I used the nix-hardware flake to simplify things.

The worst part was the compilation of the Linux kernel, that took hours on the surface. Eventually, I used the remote nix build feature to compile on a more capable computer.

I have a Microsoft Surface 7 running NixOS. Everything works, even touch/pen

If you are using Unity you can check this online session to get started integrating ROS in Unity.

My goal is to figure out a system where I can declare the shape of a robot like this (armature size, number of joints, offsets etc) to create a virtual model of the robot.

This sounds like URDF.

Now, I’m sure there are systems and packages that do all the math for this already, so what tools/libraries do you guys use to do modeling like this?

It is normal to use ROS to send instructions and receive feedback from robots, you can also setup a simulated environment with ROS and Gazebo.

ROS can be a bit rough to get into, if you need any help, you can post on the ROS community.

I use EndeavourOS with Hyprland on my laptop but I am considering trying VanillaOS (once they move to Debian base). On desktop I have Ubuntu 20.04 and EndeavourOS (both on Gnome)