Linux

Also on top of what other folks are saying, making a complete modern computer is really fucking hard.

No one is making a 3ghz CPU in their garage. Maybe folks are assembling stm32, or pis, or whatever into their own pcbs, but the machines that make the chips just aren't hobby level yet. You just have to buy some stuff.

Maybe that's not your point. Maybe you're okay with the processor being closed because it is fucking hard to make.

Beyond the hardware now we're talking making your own drivers and shit. There are resources out there like zephyr, but there's millions of devices that aren't covered.

Try writing your own SPI interface for an established MCU and a common periferal. Make sure you include crc, don't skip it. Maybe skimp and do i2c. It's fucking hard.

Years and years ago I built my own 16 bit computer from the nand gates up. ALU, etc, all built from scratch. Wrote the assembler, then wrote a compiler for a lightweight object oriented language. Built the OS, network stack, etc. At the end of the day I had a really neat, absolutely useless computer. The knowledge was what I wanted, not a usable computer.

Building something actually useful, and modern takes so much more work. I could never even make a dent in the hour, max, I have a day outside of work and family. Plus, I worked in technology for 25 years, ended as director of engineering before fully leaving tech behind and taking a leadership position.

I've done so much tech work. I'm ready to spend my down time in nature, and watching birds, and skiing.

Some people are trying (RISC-V for instance) but as others pointed out it's really really hard, especially if you want to make the whole computer free and open source.
First you need an architecture for pretty much all components if you want it to be truly free (how the CPU, ram, motherboard, etc. work, on paper).
Then you need to manufacture these components, and making a modern CPU is insanely complex, even more so when you have a brand new architecture.
Then you need software (firmware, drivers, etc.), and again, on a new architecture, stuff will work differently than it does on existing stuff. So people need to learn how to work on your platform to make software. And obviously you need to make it available to people by selling it somehow.
It's technically doable but the investment (both monetary and humanly) would be massive and not really something anyone can start on their own as a hobby.

Because money

To add to what has already been said about it taking a large effort, the follow up question is then, why don't governments fund all this effort publicly through taxes, like what is done with roads, scientific research, education, healthcare?

Well the short answer is that high-performance computing specifically is a strategic resource. Publicly funding roads only benefits the country doing the funding, so that is an easy decision to make. Meanwhile, much of the publicly funded scientific research has minimal to no strategic value (or may only be of value in states capable of that investment in the first place), so this is also an easy decision to make. But giving away technological investments in strategic ressources to rival states is a pretty bad move.

I saw a snake-oil kickstarter for one of these about ten years ago.

I used to use the Trisquel forums, Trisquel being a fully-free operating system and at the time the only one that could be installed by a total novice. There was a guy there, Chris, who was heavily involved with the company ThinkPenguin. Chris seemed genuinely passionate about free software and actually seemed pretty genuine when plugging his products, he'd point out the specific points where his products failed to be fully free and sometimes give examples of competitors who could do better and some justification for why he didn't feel it was realistic for ThinkPenguin to match that. I had some respect for him and some of the stuff he wrote on that forum really helped me understand the movement better.

Anyway, like ten years ago someone made a post about a kickstarter for a new company called Purism, which was fundraising to build a fully free high-end laptop I think by the end of that calendar year. A couple hours later the CEO of Purism (his name was Todd) found his way to that thread and explained to us how exciting this was and he intends to use Trisquel as the operating system and we should totally support this financially, blah blah blah. He's giving lengthy replies to every single comment made in that thread. At some point Chris writes an extremely extensive response about why every detail Todd has promised does not seem realistic, including recognizing from the kickstarter photos exactly which computer Todd intended to use as a base and why he felt that choice made no sense. I didn't really understand any of the details here to be honest, but yeah. Todd gives a one-sentence reply to Chris' post where he addresses zero of Chris' points and instead simply tells us that Chris is slandering his project because Chris is afraid of seeing a competitor succeed and doesn't actually care about free software.

At that point I didn't really need to understand the finer points to figure out which one of the two was more reliable. It was so blatantly transparent that Purism became a running joke in the forums.

Todd obviously ended up backtracking on virtually everything, using a brilliant scheme of weakening the promises in the kickstarter description over and over and over and dodging questions about that. He made a bunch of petitions to the FSF to certify his stuff on the grounds that their certification requirements (all those details initially promised for his laptops) were unrealistic to achieve. No shit. He also created an online (change.org? not sure about that) petition to Intel, which was sure-fire going to work, I'm pretty confident Intel did remove their management engine because I definitely would have heard more about that if Intel inexplicably decided to ignore that change.org petition.

Oh yeah, and on top of that, because Trisquel was the only FSF-endorsed distribution that was realistic for general-purpose use, he also ended up blowing a bunch of the funding to make his own distro (called "PureOS") because if he stuck with using Trisquel his customers could easily end up on a forum where his products weren't taken seriously.

Anyway, his initial kickstarter got like $600,000. He did release a laptop which was functional but not really different from things other companies like Los Alamos and ThinkPenguin had been doing for a while. A few years later he promised a fully libre phone and I think got even more for that than the laptop kickstarter. Last I heard only a very tiny fraction of the orders had actually been filled, and people were upset about that because it was already a few years late and also the company was desperately trying to remove all evidence that full refunds on request had been promised for the first couple years of preorders. Also the phones remained like six times as expensive as the (at the time) new pinephones and only functional for people who were extremely generous with how they define the word "functional".

I'll admit I did find some entertainment in this, but overall this shit was really depressing because not only could the funding Purism got have gone to other projects, but, more significantly, everyone who got scammed will be much more hesitant about supporting libre projects in general.

edit: Just checked /r/purism, the sidebar reads "PLEASE! Read at least 10 posts here before considering whether to place a Librem order! :) System76 is also a great alternative for Linux laptops." Sounds like a community of happy customers.

https://en.wikipedia.org/wiki/OpenRISC they kind of have

RISC-V is open source, fwiw.

The technology required to make a modern computer is, to say the least, not easily accessible. There are very few places we're chips are made. A handful on the planet. I mean in large quantities.

Otherwise you have laboratories mostly that have the tools to make the chips.

It is technically possible to make a free computer. But it will be much more expensive and much worse. So why bother?

risc-v?

They already did: https://www.commanderx16.com/

you just probably want something better.

and that is the problem building higher performance requires more advanced lithography and that is expensive and until recently was not even an option for a hobbyist (without taking a mortgage on their house).

Given current stagnation, you need only wait about 10 years for that viable option.

MNT Research

People are kinda working on it. The hardware isn't FOS but openPOWER and people like this guy: https://www.devever.net/~hl/ortega are making foss firmware possible.

I think because such an undertaking would require a wide breadth of extremely specialized knowledge. It would require intense coordination of many experts to work together over many years, all to design something that:

1. Will eventually be obsolete within a few years
2. Is outside the realm of replicability for individuals (I never heard of anyone with a nanometer-scale photolithography room in their house)

Item 1 is OK for hobbyists, who might value open source over new-ness, but item 2 all but guarantees that only big corporations can actually get involved. They don't care about free and open source. They just want a computing platform that their engineers can develop a product for. As long as there's enough documentation for their goals, open source is irrelevant.

The power of modern computing comes partly in how it enables abstraction. You don't need to understand the physics of electrons through a transistor to write a video game. Overall, the open source community has generally converged on the idea that abstracting away the really hard stuff is an acceptable tradeoff.

Would microcontroller count? Arduino Uno got the entire schematics out in the open. Even the core component, the ATMega processor is pretty well documented.

I'm keeping an eye on this System 76 is creating a new laptop. Not that every hardware well be open source, but whatever you get

Pine64.org?

Investment... It's a bit too simple to just say money, but investment wraps it up better. Chips may not be open source, but they are physically there to be taken apart and reproduced. That's what a lot of those Chinese knockoff chips are (baring the ones where the designs are outright stolen). The only thing that stops you from doing the same thing as those bootleg fabs is being willing to soak time and resources into the project. It's just a big project. Like a Bloomfield i7 (which is old and fairly large) has 731 million transistors in it...