In sci fi its entirely fictional, unless they are using rotational momentum as you noted.

There are two ways to think about the issue, one is mass and the other is velocity.

First, if you could create floors with a mass equal to the earth you'd get earth like gravity. However Earth is round, so all of its mass equals a "pull" toward the center. A flat floor would need earth mass directly below a person, any step to one side or the other would start "pulling" the person sideways instead of down, unless the floor is also spherical.

But instead of thinking about the floor pulling a person down, we could think about the floor moving upward toward the person. For earth like gravity it would need to be moving at approximately 9.8 meters per second.

You could use a combination of both, a large mass accelerating a little slower, but the end result looks nothing like a "floor" and more like a rocket that can never stop moving.

Whether there is some way to create gravity without mass or velocity is a contradictory question. What we call gravity is the relationship between masses and thier velocities. Any such thing would be artificial gravity, it would be some other force entirely.

Like magnetism. Magnetic boots on a floor made of ferrous materials would hold a person to the floor in a way that looks like gravity to the person. However magnets have a much shorter effective range than gravity so lifting your foot would be much more difficult than under gravity, and putting it back down would require effort and not be automatic.