MagoSaronno aka TimeToKeyBoard released the open-source Keyther, a true split keyboard with RJ45 connectors and Ethernet cables.
I want to share with you my Keyther keyboard. No TRRS, no diodes. (…) The Keyther keyboard represents an attempt at perfecting the already great Cantor Classic. The name comes from the combination of the substantives Keyboard and Ethernet, due to the use of an RJ45 socket – TimeToKeyBoard.
Introducing RJ45 (Ethernet) sockets increases security in the event of disconnection and allows hot-plugging of the slave half. (On the other hand: TRRS is more compact and cables in general may be more flexible.)
Specs
42 keys (6x3+3)
Hot-swap Choc V1 switches
STM32F401CC BlackPill controllers
RJ45 sockets & straight-through Ethernet cable
handedness by pin
Attention! The Keyther was designed to be used with straight-through cables, not the crossover ones. Always check the cable type before connecting the two halves.