Can I install 2 multiplus 2 5KVA one on phase L1-L2 and one on phase L1-L3 by a 3*230VAC grid (Belgium delta grid), off course there must remain 120 degrees between the phases.
Not officialy supported, but has been done before, you could also contact a local official victron dealer in belgium for help
I’ve seen something from Victron on this, that yes this can be done. The pair are configured as 2 out of 3 in a 3 phase set up. The information I’ve seen notes that a 3rd inverter should NOT be included, as the 3rd phase is generated by the combination of the 2 inverters.