I realize hardware is vast. So let's take the example of a bike (looks more approachable than a smartphone chip).

"Open source bike" on Google gives me this result : https://bicycles.stackexchange.com/questions/2881/are-there-open-source-bikes. It's very interesting, but just scratches the surface.

Can projects be hosted on Github ? Why can't you find something like github.com/myBikeBrand/weaselBike that would have 2000 stars, issues and PRs ?

What's the best editor for each diverse physical part of the bike ? Can they be written in code ? Or exported to text files that enable collaboration through git ? Is the fact that a vector file diff is not readable by a human a problem for collaboration, Github would be lacking a visualisation layer ? Is https://wikifactory.com aiming at that use case ?

I guess "yarn install" would be replaced by "here is the shopping list, have fun" and "yarn start" would be "find a lab, use their tools and assemble your bike according to these instructions".

Is it the order of magnitude higher for each build iteration in terms of time, cost that makes it impractical ?

Complexity doesn't look like a problem. Some websites are far more complex to build from scratch than a simple functionning bike. Is it that most software parts are fully automated (no human involved to instantiate a new DB with a schema tailored for my needs), but hardware isn't (1 hour to change the shape of my saddle but months to make it produced by a factory) ? Which kind of hardware parts can be 3D printed ?

What would be the equivalent of "yarn test" ? Virtual assembling, stress–strain and crash tests ? What's the CircleCI for this ?