2.11 is an ancestor to FreeBSD, as explained in this wikipedia page. IIRC, this is one of the last or the last release to not require an MMU unit, which I think is why retrobsd rely on it for simple microcontrollers.
Very cool project. I looked for some pic32 powered boards, thinking I could use a new hardware genre to fit (functionality-wise) in between the Pi and the Arduino (I currently use Photon boards for that service niche) - but the price point on the boards I found did not match my niche. Maybe I missed a better deal someplace. Of course it's an apples and oranges comparison since the Photon runs lowly FreeRTOS. Sure would be nice to have someBSD on an MCU.
Maybe someone can do a retro-port for the open-hardware siFive RISC V boards (the FreeBSD foundation page has a blurb about RISC V, but related to current FreeBSD, and not for MCUs). Oh well.