https://www.gamespot.com/articles/psa-you-cant-unlink-your-nintendo-switch-account-a/1100-6461802/

After several delays, Nintendo will finally roll out its online subscription service for Switch this week. The service will arrive alongside the console's 6.0 update on September 18 in North America (September 19 in Europe), which makes this your last chance to ensure the right Nintendo Account is linked to your Switch user profile if you happen to share the console with other users.

According to Nintendo, players will no longer be able to unlink their Nintendo Account from their Switch user profile after the 6.0 update is released. The company sent out the following statement via email providing further details: