Successfully achieved some level of fermentation using the contents of a single pod. Attached a photo of one of the seeds cut open. When I did this same 'cut test' a few days ago, the seeds were sort of grey with a ring of vibrant purple on the inside. Now they are closer to a deep brown.
Deep brown is what you want. They seem like they're not *quite* there yet (still a little bit of a purple tint), so I *could* ferment them more, but I don't want to risk over fermentation, especially because I've never done this before and don't want to ruin it. If the final chocolate flavor is a bit weaker than what it could be that's fine.
I looked up the temperature the beans tend to reach during fermentation, set a sous vide bath to a temperature within that range (116 F), then put a glass fermentation jar in the sous vide bath (with the seeds in the jar). Shook it every couple days, drained excess liquid, and looked for any signs of mold etc. I had the sous vide running and the water heated the entire fermentation (a week and a few days). Some aluminum foil did a great job of controlling evaporation from the sous vide bath.
Roasting now in the oven (300 F for 90 minutes) then will peel off the outer coating and grind the nibs. I know there are limits to how well you can do that without specialized equipment but I'm okay with it being grainy.
Very much enjoying the process, and the other members of the household are also finding it interesting. Will also be a fun thing to mention that I did in future conversations.