If you plan to create a product using Arduino s/w, you will need to closely examine the s/w licensing requirements.
Due to GPL/LGPL licensing requirements and technical issues with the Arduino IDE, using Arduino with closed source in products is very difficult if not impossible. It is impossible if the IDE is used to build the code.
Currently, the only way to resolve this if using the IDE, is to release the code inside the Arduino as open source.
If using closed source and not using the IDE for the building, it is possible but you will have to supply the tools needed to do the build as well as the source code to all the non closed source used in the products and provide a way for users of the product to be able to update the f/w image inside the product.
Make sure to consider this if going down that path.
In terms of providing some sort of guidance for low cost devices, as ZinggJM stated, it would be quite difficult given how rapidly things may change.
But if doing it, rather than github, I'd think something like a wiki would be appropriate.
One big issue is that peoples technical skills can very widely, so while not having documentation may be a deal breaker issue for some, it may not be a problem at all for others.
Well remember that the arduino is mainly a convenience. At least to me. Its a great sandbox tool for implementing a design, and with cheap boards available, (such as the many cheap NANO clones, which also I think folks would like to know about), it certainly is a fine for prototyping. And lets face it, typically any number of SOCs or MCUs can be used to implement the same product. If I prototype something with the arduinno, there's little reason to stay with that board after that if legal or licensing issues are a thorn in the side.
Also, as I mentioned to another responder, vendors may change quickly, but boards and specs usually have enough longevity to allow many interested folks to benefit. I've seen this in all areas of electronics, not just peripherals useful for arduinno interfaces.
Example. Consider the value of just one post explaining some LCD display with easy old style "modem like commands", and a well defined serial interface, is available on ali-express for 25¢/each, including shipping. Typically when you look at such a listing you'll find many other vendors carrying the same item. If the post included some scarce documentation, or clarifications that the poster discovered after successfully experimenting with the device, that makes it useful to many folks with a broad range of experience. And if there are only 1000 pcs available in all of China, and 100 forum members are able to get 10 each, I'd say even if the post later had to be marked "obsolete", or "no longer available", it still would have been worth the bytes taken up on the forum for the many users it helped.