I googled a lot to find the right registers, but most of the info I found wasn’t right for my inverter. In the end, I found this document (translated from Chinese apparently) which lists everything and is mostly correct: https://www.scss.tcd.ie/coghlan/Elios4you/RS485_MODBUS-Hybrid-BACoghlan-201811228-1854.pdf
I think one could replicate the entire functionality of the Ginlong-app in OpenHab, but without the 5-minute update delay. I’m only reading a few registers at the moment (current production/consumption, battery percentage, …). Not sure if I should read more the way I’m currently doing or try to get the Modbus-binding to work…