Isolation Transformer

Actually, if wired properly, the inverter shouldn't trip the GFCI even if permanently bonded.
My Victron inverter is, in fact - also because one of its functionalities it the "top up" of dockside AC supply if and when there's a peak AC demand onboard that exceeds the dock line capacity, like upon airco compressor startup, typically.
And that can only be done if it's active at all time, also while dockside AC is connected.