To install the combined NSP, UPDATE, and DLC files, your Switch (either an unpatched V1, a modded V2, or a Mariko unit running Atmosphere or SX OS) must be on firmware (ideally 16.0.3 for the latest DLC). You will need updated SigPatches to bypass titlekey verification. Without these, even a correct NSP will fail to launch.
New challenges, moves, and collectible "Mastery" items. Sonic Frontiers Switch NSP UPDATE DLC
Sonic Frontiers is the "breath of fresh air" the series needed. On Switch, it is the weakest version visually, but it remains fully playable and mechanically identical to other versions. If you enjoy exploration and fast-paced combat, the added DLC makes this the most "complete" Sonic game in years. To install the combined NSP, UPDATE, and DLC