Can you write to each other via Nintendo Switch or are there consoles where you can do that?
With the nintendo ds there's definitely a chat function
Not on the Switch itself, but in some games. I only know of the 3ds of other consoles, even if the PS4 or XBox could have it.
So you can e.g. Write together in Animal Crossing. You can write to them once while you're meeting or when a friend in Animal Crossing is also online. You can also use the app on your smartphone, which makes writing easier. I don't know if it works like that on the Switch and with which games.
