Downloadable Content in Donkey Kong games can either be downloaded for free in Nintendo 3DS or get purchsed in Nintendo Switch consoles. Once you get all DLCs from this series, you can start getting used to them to make Donkey Kong games more fun to play. Donkey Kong games exclusive in eShop are also considered DLC. The list of DLC for Donkey Kong series is very short and if you already managed to get them for this series before March 27, 2023, then you should be good to go at this point.
To learn about the downloadable content in the 3DS version of Mario vs. Donkey Kong: Tipping Stars, see Mario vs. Donkey Kong: Tipping Stars (3DS) DLC.
Mario & Donkey Kong: Minis on the Move that is exclusive in the 3DS eShop is considered DLC. For information about a 100% completion of it, refer to Mario & Donkey Kong: Minis on the Move 100% Completion.
Mini Mario & Friends: amiibo Challenge that is exclusive in the 3DS and Wii eShops is considered DLC. For information about a 100% completion of it, refer to Mini Mario & Friends: amiibo Challenge 100% Completion.
Donkey Kong Adventure in Mario + Rabbids Kingdom Battle is considered Donkey Kong DLC even though it is a DLC part belonging to the Mario series. To learn more about a 100% Completion of this DLC, refer to Donkey Kong Adventure (Mario + Rabbids Kingdom Battle) 100% Completion.