It doesn't work at all. Even in marinas (stationary) it has issues - out at sea or even at anchor you can forget about it. There are also problems with them not liking you moving around. Related article: https://seabits.com/using-starlink-aboard-and-in-a-marina/

There may be a mobile base unit at some point in the future, but it will be comparable to the current Fleetbroadband units and therefore too power hungry and too big for your average cruising sailboat. Essentially you need a motorized dish which tracks and counteracts boat movements the entire time it's active. That's what is inside those Inmarsat domes you can sometimes see on big racing boats with satellite uplinks like the Volvo Ocean Race.

It wouldn't work well since the hardware isn't designed for this purpose and coverage is focused on US land.