Animal Crossing: New Horizons does not support Switch Online saves, and if your system becomes damaged or is lost, you can only recover your saved data once.
Nintendo said previously it was planning to have a save backup function available to Switch Online users for Animal Crossing: New Horizons, but today's Direct only said it was still being looked into.
As it stands now, according to the fine print which appeared on the screen (thanks, Nintendo Everything): “Nintendo Switch Online members can only have save data recovered one time due to loss or damage of the system.”
Again today, Nintendo promised more information on this service after the game's launch.
As it stands now, you won’t be able to transfer save data from one Switch to another should your console stop working. All saves are stored on the consoles itself.
It’s thought the reason for the inability to transfer saves or the game from one Switch to another has to do with only one island allowed per console due to the fact multiple user accounts will share the same island.
Hopefully, Nintendo has found a way to work around this.
The game releases for Switch on March 20.