MKS TinyBee (ESP32) – MCU not showing in Klipper menuconfig / Cannot build .bin

[cardoc]

The ESP32 MCU is not supported by Klipper.

There is an experimental fork that claims to work but we know nothing about it.
Also see:

MKS Tinybee

I’m shopping for a new board for a 3D printer and a popular board that I can easily get is the MKS Tinybee. It uses an ESP32 as MCU and shift registers (74HC595) as port expanders. I found a fork of the Klipper MCU firmware for ESP32 here, so that should work. But as far as I can see Klipper only supports I2C port expanders, specifically the SX1509? And changing that doesn’t seem easy - in fact I don’t even understand how currently a stepper controlled through an SX1509 would work, the SX1509…