Yes. The DLC NSP requires at least Update v1.6. For stability, v1.8 is strongly recommended. If you try to load the DLC on v1.0, the game will crash on the title screen.
The DOOM Eternal update on Switch (NSP) is available now and can be downloaded via the Nintendo eShop. The update is approximately [insert size] GB in size and requires [insert version] GB of free space. doom eternal switch nsp update dlc upd