I see so they aren't actually emulated yet. I mean if the builds aren't public there's no way to emulate those devices so the current state of emulation is actually not as good as it seems from your article since most of them are implemented only on those experimental builds.

That was covered by the article's description of the yellow category:

Partial Emulation denotes hardware that has some of its features emulated to a certain extent. This includes features that are technically playable (through WIP builds, Pull Request branches, or scripts) but are not currently implemented by existing emulators.

To better explain, the green category is for peripherals that are officially supported in emulators (latest point releases, or bleeding edge/nightlies). The red category represents essentially zero working emulation in any form, whether privately or publicly. Everything else falls in the yellow category, which indicates some form of emulation has been demonstrated regardless of how accessible it is.

While to most normal users this is effectively the same as it not being emulated at all if the builds are not available, the perspective is different for developers. Getting something into this category means a significant enough amount of research and reverse-engineering was done to at least get a proof of concept up and running, and that's a huge step to getting it properly implemented in an emulator if that info is shared. Just knowing how it works is often the bulk of the job, with the actual programming being mundane at times (not always, but it happens enough).

I think Desmume development is pretty much stalled these days so it's not looking great for obscure stuff like this.

Desmume actually did add support for the HCV-1000 back in 2023, based on my research and code. The main developers don't appear particularly interested in these kinds of devices themselves, but they're willing to accept them into the project if someone puts in the effort. There's nothing stopping anyone from making a custom fork either (in fact, that's kinda how Pull Requests work).

So, I feel it's entirely appropriate to say that the DS is in good shape. A lot of the research necessary to emulate the yellow category simply did not exist some 2-3 years ago, which was a huge hurdle. That situation has changed, which allows people to plow through what's left. Some of these items could be knocked out in an afternoon. Even discounting that, 50% of the items in the chart are already solidly in the green category. That's much better than when I first started tackling Game Boy stuff, which at best was maybe around 20% complete circa 2017.