Korg’s answer is the NanoKey Fold ... The NanoKey Fold has both USB-C and TRS-MIDI outputs, and comes supplied with a TRS-to-MIDI DIN adapter. There’s no Bluetooth connectivity - a cost ...

Using a Korg nanoKEY2 USB MIDI controller as base for the device, [Geordie] took it apart and added a Raspberry Pi Zero W, a power bank to, well, power it, and a USB hub to connect a likewise ...