Nintendo Switch's Pokémon Legends: Arceus will be adding a new type of lore-friendly Poké Ball, Strange Balls, as part of its upcoming Pokémon Home compatibility update. Pokémon Legends: Arceus introduced new Poké Balls due to the fact that it's set in the distant past of the Pokémon world, which is unfamiliar compared to the era where the other mainline Pokémon games take place.
The events of Pokémon Legends: Arceus happen during a time when modern Poké Balls hadn't been invented yet. Instead, the Pokémon Trainers of the world used steam-powered Poké Balls to capture their targets. Part of the game's gimmick involves showing how Pokémon Trainers operated in the era before futuristic technology made everything so convenient, with the Pokédex being a physical book, and Pokémon being stored in farms, rather than a PC box.
The fact that Pokémon Legends: Arceus happens at such a different point in time creates a problem when trading with other games. Pokémon games don't support Pokémon Home at launch, meaning fans have to wait months before they can bring Pokémon in from their other games. That wait is about to be over for the recent Pokémon games, as the official Pokémon UK website has announced that Pokémon BDSP and Pokémon Legends: Arceus will receive Pokémon Home support soon, and that Strange Balls will be added to Pokémon Legends: Arceus to accommodate Pokémon from outside of the game. The website confirms that transferring Pokémon from BDSP and Sword and Shield to Legends: Arceus means they'll show up in-game in a Strange Ball, while transferring Pokémon from Legends: Arceus will see them arrive in-game in regular Poké Balls.
Strange Balls are bright green Poké Balls with a whitish tint in the center. Pokémon Legends: Arceus dataminers discovered Strange Balls in the past, but their true purpose was unknown. Many speculated that their inclusion may be related to an unannounced DLC for the game, though others were convinced that Strange Balls were part of the title's future integration with the Pokémon Home storage and transfer system, as has proven to be the case.
The existence of Strange Balls doesn't quite resolve the time paradox established by futuristic Poké Balls appearing in the ancient Hisui region, and they were likely created to cut down on development time. Pokémon Legends: Arceus features unique Poké Balls that are more primitive than the classic Poké Ball design, so it would have been a pain to include all of the modern variants from games like Pokémon BDSP. The Pokémon series isn't exactly strict with its canon, so the presence of Strange Balls can just be chalked up as being another one of Pokémon Legends: Arceus' unsolved mysteries that will never be addressed in future Pokémon games.
Source: Pokémon UK