Factorying reset nintendo switch - what's the trick?

if you're keeping it and just want a clean slate, there's a gentler option. turn it off, hold volume up and volume down, then press power. that opens maintenance mode, and restore factory settings without deleting save data wipes the system but keeps your saves. if it's going to someone else, use the full one.

System Settings, System, Formatting Options, Initialize Console. that wipes everything. if it's going to someone else, go to the eshop first and deregister it as your primary console, saves a headache later. if the console won't boot into the menu, power it off, hold volume up and down together and press power - that gets you maintenance mode, which also has a reset that keeps your saves.