I think bluepadraig maybe has solved this already but was for an earlier version and i wanted to check that his solution was still valid for the hestia pi one.
So you cant send L and the other 230v line which is normally shorted black to dark blue if no thermostat is being used. You cant send them both to the hestia pi.
But you can power the pi via a usb (desolder the acdc transformer from the board) and then send the alternate 230v live out to the L pad on the pi and the other wire to the H pad. That is my understanding of his work around. Can you confirm this would work for the hestia pi one also? Are both usb sockets still capable of powering the pi?
Yes. I cannot really comment on the rest. HestiaPi shorts R with the appropriate terminal (heating, cooling etc) when that function is triggered as long as it is AC signal within a range (at least 24-240V AC).