Is there a word for a non-geek?
Solution 1:
Layman could be used to describe someone who is "untrained or lacks knowledge of a subject".
Solution 2:
In terms of an antonym jock (as in high school sports hero, not someone from Scotland) is at the opposite pole of the social spectrum to geek.
If you're looking, instead, to indicate that the person simply lacks all the qualities of a geek then normal is one option, because that indicates they're in the middle of any spectrum.
I was at a geek gathering where we received a talk by a self-titled non-geek, so that seems likely to be understood by anyone.
The problem with categorising non-geeks with a single word is that geek signifies a group. Not being part of a group is not a remarkable thing, most people are not part of most groups, so you're looking for a word that describes people who don't have the properties of a geek. If someone has these properties, then they are tagged as a geek, otherwise they're not tagged.
It's not often there is a word for not having a complex set of properties.
Solution 3:
Don't use "Muggle", it is kind of specific to one particular fictional work.
And there are plenty of us who identify with "Geek" but not with that particular work. (Or in many cases with any fiction at all. Many geeks are pure tech geeks.)
This never really seems to work. Whether you try to call those outside of an in group "squares", "straights", "mundanes", "norms", "muggles" or what have you, it always ends up looking really dated, really quickly.
Non-Geek is probably the safest and most accurate.
(Heck, in its classic sense the opposite of "Geek" would be "Rube".)
Solution 4:
I often use "civilian" for this sort of thing.