If antifreeze is entering a combustion chamber you will see a very clean spark plug and piston. This will not happen to all of the plugs, just one or two.

Depending on engine hours (mileage) you also need to look at the water pump and check for failure. Hopefully, no one replaced it with non-OEM plastic vaned type.

Removeing the thermostat was a good move, but that also means that the engine should not overheat or even get close to the red zone, so long as the pump is working and the ECT sensor initiates the fan.

I encountered a post on Volvospeed where a person installed a clear plastic hose between the thermostat housing and the upper radiator hose. He could then verify that fluid was moving and the pump was good.