EEE here with 16 years experience and having to deal with compliance from day 1 of my career. I now consult on product compliance. Author you are welcome to contact me.

Disclaimer: Nothing below is meant as legally relevant compliance advice. This is just my opinion on the matter.

Going to snark:

"The testing and certification industry is odd"

Except, outside the software world, the real world, where there are real consequences, it's not really.

"The line about CES, in particular, made my hair stand up."

Why? Absolutely the unauthorised device at CES is should NOT be allowed. What if said device caused too much interference on cell phone frequencies and suddenly nobody at CES can dial the local emergency number?

If that made "your hair stand up", here's one from personal experience that will freeze your blood:

I worked as a teen for a certain electronics chain. Said chain was selling a wireless weather station imported from China. A government department that monitored the country for Earthquakes noticed that this device impinged on their frequencies. After the spectrum regulator confirmed the finding, a nice gentleman from them visited us a told us the following:

1) As of this moment this device can no longer be sold. Move it off the floor immediately (he stayed and made sure we did exactly that).

2) That we will immediately issue a recall of said device at your own cost and issue full refunds to the customers.

3) He will return when we decide on further enforcement action which may include punitive fines and recommendations for further remedial action you will need to undertake.

"In theory, it exists to serve the public good and uphold consumer protection laws."

Well here's a (very simplistic) tidbit for the author: In the US, part of the gestation and formation of standards bodies and testing was "market forces", not for the public good. It was to help protect companies from litigation. If you followed the standards, tested and certed to them, paid the fees etc you then had the standards entity bat for you in court (UL is short for Underwriters Laboratory. That name was not chosen for funsies).

"However, in reality, the labs are “too busy” to respond or reply very late and generally sound less than eager to work with you."

Well you don't sound like a serious customer. AND the Labs are not there to give you advice. They're there to do INDEPENDENT testing.

"Variations of the FCC exist in pretty much every developed economy. Putting a poorly tested hardware product on the market immediately puts a target on your back. Maybe you’ll get lucky, but chances are that someone somewhere will report you. And, unless you are operating entirely out of China, it will hurt. A lot. Both your company and maybe even you, personally."

As it should. The electromagnetic spectrum is a very precious and very limited commodity and IMO, the best regulated "commons" in human civilisation (though still not perfect). So no, you are not welcome to just urinate in it willy nilly with your hustler start up product.

"I did not want to spend so much money on testing before I validated the market or gathered a community of believers."

And there it is.

"This way, the electronic device liability will fall on the manufacturer, and the magic of friendship EULA should afford me enough protection to make this a pure software play."

No. That's not how this works.

1) I assume the author is from the US (as they speak about the FCC). I had a 30 second look at these dev boards and their instructions. There is no FCC conformity declarations or markings, so US customers can't use it.

2) It has CE and UKCA though, so customers from EU+UK (and some other countries) can buy them but the certs only cover the dev boards AS SOLD. (i.e without the authors software)

3) Author is modifying the product behavior with their software. So yes author. You are still liable. Technically, your customers are first in the line of fire. But the likely sequence of steps is: Friendly Spectrum Representative will visit them first, have a chat, ask them to stop using the device, then leave them a lone and then come for YOU.

4) What the author has actually done is "buy down" their risk. It is simply less likely that the product will become non-compliant when their software is loaded. But it is still possible. At second glance, those dev boards don't come with a power supply. What is your recommended power supply to use Author? Have you tested your setup with said power supply and have test reports at the ready for when Friendly Spectrum Person comes knocking?

5) Sure it seems clever but Friendly Spectrum Agencies actually have quite far reaching and scary powers. Don't think that your little sleight of hand here is clever and protects you. Fundamentally: You are repackaging + modifying an existing product. The steps you are taking in between to "launder" your liability are irrelevant.

Frankly, it's shit like this, that makes it harder for everyone else playing by the rules. It did actually used to be easier. There used to be exemptions for "low volume" products. But all of those were seen as loopholes and HEAVILY abused. Now these toys have been taken away, with more to follow.