Slightly off topic, but I really want an instrument that works like LinnStrument but with a synth built-in (so you can actually play it without connecting to something else).
The same Eaganmatrix engine used in the Continuum has also shown up in the Expressive E Osmose, so apparently Haken is willing to work with other companies to integrate their synth in more products -- and the result is quite an amazing device. Haken also makes a standalone Eurorack module.
I'm not sure if there's a good open-source MPE synth that's easy to port to microcontrollers. Surge is really impressive but it's not made to run on simple embedded platforms.
I know it's not quite the same thing as you're asking for, but when you dig into the linnstrument it turns out to be very hackable.
But maybe I didn't google the correct word for it.
The Disting Ex [0] Eurorack module contains nice ones and supports MPE. You'd also need a PSU [1] for it.
[0] https://expert-sleepers.co.uk/distingEX.html [1] e.g. https://frequencycentral.co.uk/product/microbus/