This site informed me about the existence of the ZMK firmware, does anyone here have any experience with that?
I used it to build a fully wireless split keyboard. Each half has a BLE-capable MCU (nice!nano). The primary half communicate with the secondary half and primary halves. It works WAY better than I thought it was. I was quite concerned about latency and the secondary half modifier keys. Instead, the biggest problem is the hot-swap sockets I got. I will go back to soldering my switches from now on.