Super SMN5 64 dumb is likely a variation or a different version of the Super SMN5 64 fan-made game. The addition of "dumb" could indicate a humorous or less serious take on the original, potentially having different or altered game mechanics.  Information about the specific changes would necessitate research within the relevant fan communities. As it's an unofficial creation, it's not a standardized game.

Super SMN5 64 dumb

Super Smash Bros. Sonic Mod