Fwiw, even just going through your software with one user can give quite a few insights about what's not obvious about it. That's not at all to say you never need more, but very few open source projects do user research in the first place, being passion projects that just scratch the developer's/s' itch. More samples is always better, definitely at n=10, but I'd also not dismiss the results and benefits of doing it!

Also, how many people you need depends heavily on whether the thing you're researching affects a lot of people. If settings has a problem that affects 40% of people, then a sample of 10 people would yield results representative of the whole population.

Sample size is a very weird, often kinda counter-intuitive topic.

If the crowd is diverse enough. Was it? The article doesn't reveal.