Downloading and installing NSP files requires a modded Nintendo Switch. This process violates Nintendo’s Terms of Service. Proceed at your own risk. We do not condone piracy; this guide is for users who own a legitimate copy of Minecraft and are extracting their own updates.
You are trying to load an old world generated before 1.21. Fix: Travel to new chunks (areas you have never visited). Alternatively, create a brand new world with the "Tricky Trials" experimental features turned ON (Settings > Experiments). Minecraft -NSP--Update 1.21.2-.rar