You still interested in building some open source smart thermostats for the people in Australia?
HestiaPi.com has the info on it and the electronics files are at https://github.com/HestiaPi/hestia-touch-pcb-dev
I'd be happy to chat if you have questions or anything. I'm pretty flexible on days & times that I can be available. Preferrably not between 00:00 and 07:00 Central Time (Chicago) though. 😅