Nintendo has started to ban the Switch consoles that are hacked to run homebrew leading to piracy or other forum of open code being run on the hardware. This means if you have already hacked your Switch, you should avoid online as much as you can or you get the risk of permanent ban from the official Nintendo servers.
The issue was first confirmed on GBATemp where a use who had a hacked Switch shared his experience with the ban. The ban message confirms that the console won’t be able to go online once Nintendo blacklists it from their network. Here is how it looks on the screen.
The error code that corresponds to this ban is 2124-4007. Those who get banned with this code can’t get into the eShop or access the online services on their Switch. They can still browse the news feed and see the updates shared there, but they won’t be able to get much use out of it online.
This ban is reportedly permanent and won’t be cancelled or removed even if you contact Nintendo. This seems to mirror the work done by Sony who also permanently banned anyone who used custom firmware on their PS3. At first, only the accounts were banned but later the whole console along with the account was banned.