Progress on the double-oh stalled in March, as did everything else in my life. But now I'm sort of getting back to a stable place and I have a good progress report!
First, I'm pleased to announce that hardware version 2.4 basically works! A few days ago, I ran a demonstration on Twitter (slightly NSFW) and invited people to sign a guestbook served from my butt (no pictures, but still NSFW simply by association). And I should have done a better job sanitizing the guestbook comments, because...well, they were susceptible to HTML injection. In a historic moment for the field of teledildonics, I was rickrolled by HaD user [arturo182].
It doesn't fully work, mind you; it turns out that the factory-reset jumper and the battery voltage detector are both connected to inputs that can't be used when WiFi is on. This required mercifully minimal changes to the routing, but it does mean waiting for another batch of PCBs. I also want to make the variable voltage output go lower than 1.3 V (its current minimum), so the double-oh can trigger low-battery warnings if necessary. This requires tweaking some resistor values that aren't behaving as I expected.
On the firmware side, I was encountering a frustrating bug with the UDP libraries in PlatformIO. Switching to the Arduino IDE immediately fixed all the bugs, but GOLLY it's not very fun to code in the Arduino IDE.