No new Pokémon, missions, or features were added. For most players, the update was seamless – applied automatically upon connecting to the internet with auto-update enabled.
If you are looking for "long content" in terms of how much time you'll spend playing, here are the general estimates from HowLongToBeat : Pokemon Legends Arceus -NSP--Atualizacao 1.1.1-...
Downloading, sharing, or distributing .nsp files of copyrighted games without owning a license is software piracy , which is illegal and violates copyright laws. Additionally, installing unauthorized .nsp files on a modified Switch console carries a high risk of bricking the device or receiving a permanent ban from Nintendo's online services. No new Pokémon, missions, or features were added
. Updates are typically small but necessary for online features. Availability: No new Pokémon