Open-source hardware is almost non-existant compared to software. There is a reason for it.

I am an electronics engineer who makes open source hardware as a hobby.

Hardware is extremely different from software. It requires substantial monetary investment.

My company last year did a dirt-cheap lowest-possible-budget prototype design and run of 10 for someone funding themselves independently. It cost 8000€ for the design and that one prototype run, and an extremely simple design at that (electronically, medical-spec mechanically).

Software you buy a system and you can develop and develop and iterate and test 1000 times and develop multiple projects on that single machine. If you sell 0 units, sure you are out a computer and a ton of personal time. Sucks, but you won’t lose your house.

If you do electronics + mechanical development, every time you iterate on the electronics, that will be 200€-1000€ please, plus test equipment. If you make a small mistake equivalent to a wrong pointer that is another 1000 down the drain.

Hardware projects, pure material-wise, can cost more than a car to develop (just going through CE and FCC compliance testing can be 2k-10k and you aren’t allowed to sell in the EU without it.

You need capital to burn. Most people would rather make a down payment on a house than develop open hardware that might never recoup just the material costs.