Last night I was able to successfully do a few test prints of the lucky cat and butterfly using the V2 (STM32F070) MCU. This means this project is drawing to a close, of sorts. Marlin main now supports the printer, V1 and V2 both click-compile for the most part. The sample config will work if I update the documented settings on how to compile, or I may update the sample config.
V3 (with auto-level) is a matter of defining the probe pin (I believe it's PA3) and configuring ABL, but to do that, I'd need to re-enable EEPROM emulation. It doesn't currently work under ST's core using the unified HAL. It's really one of the last things to be needed, and once it's done, short of adding WIFI printing to Marlin Main, and Malyan's custom GCODE, there's not much left.
I created a config for the Malyan M300 delta /MPMD and may do a test with it as an extension of this, but the delta more or less just works. We'll see once I draw the V2 work to a close.
V3 is a possibility, enabling ABL, except I don't have a V3 - I'll need to use my V1 + probe or the bl-touch I wired to a V2.
Delta is a possibility.
Soon I'll get back to the Lerdge project.