DST Switch does work in LAN mode without Nintendo Online.

I was getting conflicting information on this before I went ahead and finally bought the switch version.

For all people looking at this in the future, you can play DST on multiple switches all in LAN mode without Nintendo Online.

You can also play using tunnelers and VPNs so long as your local network is the same.

Finally, it is actually possible to play using only one copy of the game.

What you need to do is share an account that owns DST.

Have one switch set to online activation for games.

Load up the game and activate it.

This switch then needs to have its DNS settings set
to a known 90DNS server in order to block access to Nintendo’s servers.

At this point, you can load the game like normal on the 2nd switch. You should probably also DNS block it while doing this method to better ensure you don’t get banned.

At this point, both games should be running and connected to the router, so it should work as normal DST does.

There is no checking of player accounts afterwards, so you will not get booted for having 2 sessions using the game ID.

I would like to note, I am not responsible if you do get banned. I have only done this method just to make sure LAN mode actually worked before I went and bought a second license on a second Nintendo account.

If you are wondering why the DNS must be set, the switch no longer connects to routers without internet access. Simply blocking the internet to the switch at the router level will not work.

If you have other methods to block the switch from phoning home to nintendo, those other methods should also work.