I have a on-grid inverter made by Spirvent.
Unfortunately this maker does not exist any more and I cannot get any reliable info about it now.
It still works so I would not want to spent money on the new one, just to be sure that it will work in AC coupled configuration, because it is on the Victron approved list.
Is there a way to test this Spirvent reaction to frequency shifting other than connecting it on AC out and waiting for the moment that MultiPlus-II will need to lower inverter output and starts shifting the frequency?