Minecraft for Nintendo Switch doesn't allow connecting to Bedrock servers via IP. It only allows multiplayer by connecting to 1 of 5 pre-whitelsted public servers. Using docker, this repo contains everything necessary to connect your Nintendo Switch to your own private (or any other dedicated) server.
The basic premise is when your switch tries to connect to the Lifeboat Network, it is connecting to mco.lsbg.net. By running a local DNS service (bind9) and pointing the Switch to use your DNS service allows you to intercept the request to mco.lsbg.net and resolve it against your private (or any other dedicated) server's IP address
docker-compose up
docker-compose up