Smokeless powder has always been 100% legal in Wisconsin.
It is considered a black powder substitute, which is precisely what it has been for the last 110 years.
No, a black powder substitute is pyrodex or Trip Sev, or similar, which is intended for use in a muzzleloader. Smokeless powder is intended for use in a centerfire cartridge or shell. If you try and use smokeless powder in a muzzleloader you risk serious injury.
Regards, sse