Ultimately, "the edge of space" is an agreed upon convention. In other words it is essentially arbitrary, something which only humans even care about (well maybe space aliens too <grin>). Yes, there are various physical properties which can be used to define this boundary and the measurements themselves are not arbitrary, none-the-less, the choice of WHICH system of measurement to use is arbitrary.
Back in the 60's and 70's, in America, "the edge of space" was deemed to be 100 miles. It was defined this way because there was essentially no atmosphere at that altitude and because it was a nice round number to work with. This is what I was taught in school.
Now that the metric system has become prevalent, the definition has changed from 100 miles to be 100 kilometers, because the atmosphere at that height is still thin enough to be thought of as essentially a vacuum, and because under the metric system it is a nice round number.
The choice of various physical properties to justify these numbers are secondary to the fact that human brains prefer nice round numbers. We could have just as easily defined space as being above the maximum height that is achievable by a high altitude balloon, or by a bird. Or some other measure that resulted in a nice round number.
Given our earth centric view, we have always considered the presence of an atmosphere to define the absence of space, and we consider by various measures that space is roughly equivalent to a vacuum -- the only point of disagreement being the specific density at which we define the atmosphere to be at a vacuous state, and that choice is fairly arbitrary.
From that perspective I think it is reasonable to say that space extends to the surface of any planet which lacks an atmosphere.
The lowest achievable orbit is a separate matter and does not itself define where space starts. However since it is impractical to sustain an orbit inside of an atmosphere, we can use that as a way to define what is not space. In other words if you can't orbit at that altitude due to the presence of an atmosphere then you are not in space.
On a planet without an atmosphere the lowest achievable orbit has three constraints. The orbit must be high enough to clear any physical obstacles, such as mountains. And it must be slow enough to avoid achieving escape velocity for that specific planet's gravity, while also being fast enough to avoid colliding with the planet (i.e. Free-fall).
None of which is useful for defining the beginning of space itself, except in an arbitrary way. For instance on a planet with very tall mountains, the lowest achievable orbit is much higher than on a planet with a smooth surface.
The Kármán line does not easily apply to planets without an atmosphere because it is really just another way to define the point at which the atmosphere becomes so thin that it can effectively be considered to be a vacuum. Basically it is a way of saying that if the atmosphere is thick enough support an airplane then you are not in space. We could apply this to a planet without an atmosphere but that feels like a misapplication of it's intent.
More intuitively, think of an astronaut taking a Space-Walk. If the ship is in-between planets, then the astronaut experiences space in a particular way, specifically as a vacuum with extremes of light and temperature. Clearly this is Space. Now consider that same astronaut going for a walk on the moon. Beyond the addition of some rocks and some gravity, their experience of Space is identical to the one that they had while in-between planets. In both instances it is reasonable to say that the astronaut is In Space.
From which we can conclude that Space, as defined by humans, extends to the surface of the moon and any other planets (meteors etc) which lack a significant atmosphere.