If you want to go the COM Port way, just do it. To be honest, working with cables, creating own ethernet ports and screwing things in and out of a inverter scares me to death.
If there does exist a working AIO device - COM-Port, matching two cables for my inverter (H34B model) pre-assembled, LAN-Port ready to fit into a switch - I would pay for it.
If you want to go the QCells/Solax Cloud way, just tell me.