In my research I found that UTL and Ashapower are engineering focused manufacturers and have high quality offerings compared to others (that are profit based), so you most likely have a very capable inverter.
The rccb you mentioned is type AC.
I haven’t been able to find any installations on YouTube that use a two pole rccb with a inverter and a common neutral.
The conventional wisdom appears to be that if you want to use a seperate two pole rccb with an inverter, you cannot have a common neutral, you need isolated wiring.
However I did find someone that used a four pole rccb with a common neutral. They used only three poles, live from the electricity board, live from the inverter and the common neutral — so that’s one rccb for both inverter and mains ac. That’s probably the easiest solution for you.