Unless you’re wild camping, campsites have addresses. So do marinas where a ship would need to be docked more or less regularly to establish residency.

As for being a nomad, you don’t need a driver’s license or any kind of ID to wander if you’re willing to sleep rough. If you want to drive on public roadways though, you better have a primary address where the courts can send someone if you kill someone in a traffic accident and bail.

For most situations where you don't have a permanent address, your address is either the place where you receive mail or the courthouse.

In some places in the U.S. it is (or at least was until recently) illegal to be healthy and unemployed.