“Dear, how is it possible to achieve DR=0 with the RAK3172 module on an AU915 network?”
Dr0, SF12 may not be practical in some regions where there are regulatory constraints. E.g. in US a dwell time limit of 400ms on US915 limits to DR2, SF10 in practice. Au uses two bands the AU915 and AS923, if either imposes similar on air constraints then DR0 may not be possible/practical/legal…… you need to read the L-A documentation for guidance. Note L-A generally disuades heavy use of SF11/12 in general due to on air impact, limiting joining etc.