Hi. I made a new custom component that shows the state of users on Nintendo Switch Online.
The API only allows getting the state of your friends (not your own state… 
), so if you need your own state, you need to create a new account and add it as a friend.
The component adds a binary sensor for each friend in the account and shows ON if the user is online, with the game in use displayed in the attributes.
You can find the component on my GitHub: GitHub - MiguelAngelLV/ha-nintendo-switch: Nintendo Switch Online custom component for Home Assistant