I have found this issue on here recently, however though it says that it is resolved it is not. My fiance and I have been trying to play multiplayer Minecraft on Nintendo Switch for the last month and a half. However whenever the second player tries to join, that side of the screen flashes rapidly. I have tried to update the software, I have deleted and reinstalled the software, adjusted TV settings, nothing is fixing it!
Warning: Video may affect photosensitive viewers
Please indicate what version you have on the main screen in the lower right corner, and also do you use any texture packs?